This is my theory about how the game will play out.
 
 MASSIVE MASSIVE Mass Effect 1 and 2 Spoilers below. LIKE ALL OF IT SO DON"T BE DUMB AND READ IT.
 
The game sets up with, "the reapers are coming, no way to stop them from getting here" and most of the game will be to recruit all of the races/factions/mercenary groups to fight off the reaper invasion. 
 
1. Urdnot Wrex (If alive) will unite the krogans under one banner to fight the reapers.
2. The genophage will be cured so that more krogan can fight the reapers.
3. Tali Zorah (If not exiled) will recruit the flotilla to take back homeworld/give up homeworld to fight the reapers
4. Zaeed will take back control of the blue suns and will lead them when fighting the reapers.
5. Legion (if alive) will convince the hiveminded geth forces to fight the reapers
6. Jacob and Miranda will lead cerberus in fighting the reapers.
7. Mordin will reunite with Salarian Special tasks group to fight the reapers.
8. Ashley Williams will forgive Shepard and together will unite the Aliiance to fight the reapers
9. Depending on how you've treated the batarians, vorcha, hanar, volus and other species will help fight the reapers.
10. The collector facility will be used for or against fighting the reapers.
 EDIT: 11. If you didn't save the rachni you're dumb. They will help fight the reapers by ripping faces off.
Thoughts?

You forgot the Rachni.

So it'll be Dragon Age in space, then?

" You forgot the Rachni. "

" So it'll be Dragon Age in space, then? "

" @Hailinel said:

" So it'll be Dragon Age in space, then? "

Mass Effect came out before Dragon Age. "

I'm hoping it'll be more nuanced than that. I'd rather it wasn't just "oh you were nice to these people so all of ____ race will help." If anything, I hope this game introduces some damn tough decisions for Shepard to make and something more interesting than recruiting factions.

" So it'll be Dragon Age in space, then? "

" I'm hoping it'll be more nuanced than that. I'd rather it wasn't just "oh you were nice to these people so all of ____ race will help." If anything, I hope this game introduces some damn tough decisions for Shepard to make and something more interesting than recruiting factions. "

" @benjaebe said:

" I'm hoping it'll be more nuanced than that. I'd rather it wasn't just "oh you were nice to these people so all of ____ race will help." If anything, I hope this game introduces some damn tough decisions for Shepard to make and something more interesting than recruiting factions. "

Obviously, you didn't play the previous two games. Both of them revolved around "recruit ___________," and that worked damn well before. If it ain't broke, don't fix it, I guess. "

Not an unlikely possibility, I'd say.
 
Species homeworlds, here I come?

" You forgot the Rachni. "

You forgot the Elcor.

It had damn well better be about Recruit the Factions - if it's not then Mass Effect as a series will have failed. 
This is the concluding chapter, it should be mainly about wrapping up all the threads of the plot so far and should have very little (more like nothing)  to do with recruiting a new squad or gaining the loyalty of the new faction. 
 

 1. Urdnot Wrex (If alive) will unite the krogans under one banner to fight the reapers.

2. The genophage will be cured so that more krogan can fight the reapers.

3. Tali Zorah (If not exiled) will recruit the flotilla to take back homeworld/give up homeworld to fight the reapers

 4. Zaeed will take back control of the blue suns and will lead them when fighting the reapers.

5. Legion (if alive) will convince the hiveminded geth forces to fight the reapers

6. Jacob and Miranda will lead cerberus in fighting the reapers.

7. Mordin will reunite with Salarian Special tasks group to fight the reapers.

8. Ashley Williams will forgive Shepard and together will unite the Aliiance to fight the reapers

9. Depending on how you've treated the batarians, vorcha, hanar, volus and other species will help fight the reapers.

10. The collector facility will be used for or against fighting the reapers. 

Well, yeah, "Recruit the Factions" seems like the obvious structure for the next game doesn't it?  I hope they're a bit more subtle about it than just "Collect the 4 x!" which has been the structure for Dragon Age (allies), KOTOR (star maps), Jade Empire (amulet pieces), NWN (plague cure ingredients), Mass Effect (pieces of investigation)...
 
It could very easily turn out to be Dragon Age in space, and that would be a lazy and weak way to end the trilogy imo.

" @FluxWaveZ said:

" You forgot the Rachni. "

It'd be cool if they would figure prominently but they probably won't.  It'll probably come down to a colony getting saved that otherwise wouldn't if you spared the rachni.   "

I agree with most of these. Tali, Legion, and Wrex/Grunt will probably be the most important in terms of the recruiting factions storyline.
 
While I would like Zaeed coming back in such a way, I'm doubting it. Same for Mordin. Can't see Jacob or Miranda being too involved, either. Ashley/Kaiden? Maybe.
 
I think, apart from that, Samara could show up as someone that will make recruiting the Asari easier or some such. The word of a Justicar and all that. Also, I think the new party members or important characters will be characters involved with recruiting/uniting a race. So we'll probably see a new batarian, salarian, and turian. We'll also probably (unfortunately) see replacements for important characters that died.

more recruiting? eh =/ 
 
wow i just noticed something.. i sucked at Mass Effect!     
1. i killed Wrex 
2.  Tali's exiled 
3. Mordin's dead 
4. Garrus's dead 
5. Legion is dead 
 
 
whats wrong with me? ;(

" @BitterAlmond said:

" @benjaebe said:

" I'm hoping it'll be more nuanced than that. I'd rather it wasn't just "oh you were nice to these people so all of ____ race will help." If anything, I hope this game introduces some damn tough decisions for Shepard to make and something more interesting than recruiting factions. "

Obviously, you didn't play the previous two games. Both of them revolved around "recruit ___________," and that worked damn well before. If it ain't broke, don't fix it, I guess. "

Mass Effect hardly involved recruiting anyone - you were given your entire team before you left the Citadel (minus Liara) and spent a lot of time doing regular missions. Mass Effect 2, on the other hand, revolved entirely around amassing a team and going on a suicide mission. It'd be kind of redundant for the third game to make you more or less do the same thing again. "

" @SteamPunkJin: Doubt that a huge jump like that will happen, due to one of the (or the?) last shots of Mass Effect 2 being of those shit-ton of reapers coming from Outer Space.  Seems like a pretty urgent thing. "

" @ninjakiller said:

" @FluxWaveZ said:

" You forgot the Rachni. "

It'd be cool if they would figure prominently but they probably won't.  It'll probably come down to a colony getting saved that otherwise wouldn't if you spared the rachni.   "

They'll show up I hope, but my codex knowledge is weak, how organized are the Rachni? Are they worth calling a faction or are they just animals? "

 @SteamPunkJin said:

" @benjaebe said:

" @BitterAlmond said:

" @benjaebe said:

" I'm hoping it'll be more nuanced than that. I'd rather it wasn't just "oh you were nice to these people so all of ____ race will help." If anything, I hope this game introduces some damn tough decisions for Shepard to make and something more interesting than recruiting factions. "

Obviously, you didn't play the previous two games. Both of them revolved around "recruit ___________," and that worked damn well before. If it ain't broke, don't fix it, I guess. "

Mass Effect hardly involved recruiting anyone - you were given your entire team before you left the Citadel (minus Liara) and spent a lot of time doing regular missions. Mass Effect 2, on the other hand, revolved entirely around amassing a team and going on a suicide mission. It'd be kind of redundant for the third game to make you more or less do the same thing again. "

You might have missed the part where you actively recruit Garrus and Wrex, it's possible to leave the Citadel without them, skip finding Liara and wind up with just  Kaiden/Ashely/Tali."

Their is only one proper mission in the game where you actively seek out a squad mate in ME1 and thats Liara the rest is story progression

That seems like the easiest route considering how Bioware designs games, and I don't doubt it will be the one taken. Although, it will be kind of lame if that's going to be the only intricacy to the plot.

5. Legion (if alive) will convince the hiveminded geth forces to fight the reapers"

" Their is only one proper mission in the game where you actively seek out a squad mate in ME1 and thats Liara the rest is story progression "

I demand that Mass Effect 3 end the same way as the new fallout games. With a bunch of crappy still images, some voice over, and no closure. It would be so bad that I would laugh endlessly and await the millions of enraged forum posts with some sort of sick catharsis.

"I demand that Mass Effect 3 end the same way as the new fallout games. With a bunch of crappy still images, some voice over, and no closure. It would be so bad that I would laugh endlessly and await the millions of enraged forum posts with some sort of sick catharsis. "

" @Mikemcn said:

" @ninjakiller said:

" @FluxWaveZ said:

" You forgot the Rachni. "

It'd be cool if they would figure prominently but they probably won't.  It'll probably come down to a colony getting saved that otherwise wouldn't if you spared the rachni.   "

They'll show up I hope, but my codex knowledge is weak, how organized are the Rachni? Are they worth calling a faction or are they just animals? "

Unknown.  The giant bugs you spared from ME1 that you learn nothing more about really other than a message from them in ME2 promising their help when the darkness comes.   "

"@RVonE: Yeah, they just have a new race to fight...and they they just don't mention the reapers or anything in the previous Mass Effect games ever!  EDIT: The new race should be called "The Receivers" or "the Shippers" "

" @benjaebe said:

" I'm hoping it'll be more nuanced than that. I'd rather it wasn't just "oh you were nice to these people so all of ____ race will help." If anything, I hope this game introduces some damn tough decisions for Shepard to make and something more interesting than recruiting factions. "

Obviously, you didn't play the previous two games. Both of them revolved around "recruit ___________," and that worked damn well before. If it ain't broke, don't fix it, I guess. "

 But either way shepard is fucking going to die!!!  "

Its generally assumed (at least by me) that everyone you mentioned/everyone in the whole universe that arent evil-geth are going to team up to fight the reapers. I dont see why fuck any of the races is going to not fight them, seeing as how they're going to wipe every living thing out in the galaxy...again

I hate this idea. I just want a story that revolves around the world and things actually happening like ME1, not recruiting bullshit like ME2.

I hope they just scrap Wrex. I'm tired of being constantly reminded that I let him dead. YEAH, I KNOW I FUCKED UP! FUCK YOU BIOWARE!

"I hope they just scrap Wrex. I'm tired of being constantly reminded that I let him dead. YEAH, I KNOW I FUCKED UP! FUCK YOU BIOWARE! "

Looking at the massive amount of reapers that the fleet has, recruiting all the factions is still not enough and they don't have enough time to start building a powerful new fleet even using the best technology they had developed since the battle of the Citadel.
My theory is that the Reapers have been doing the genocide cycle for more than one galaxy, a LOT of galaxies and maybe there are other cases where there is someone like Shepard trying to prevent them from coming back or that at least have some clues about this old machines existence.
My idea is that there is a Reaper HQ somewhere hidden in darkspace where they have special relays that they use to jump to places like the Milk Way Citadel. Shepard would use the Citadel relay functionality to go to this HQ that is now empty because the fleet is travelling the old fashion way without using any relay jump. There he will send a message to every galaxy, with his knowledge that includes the prothean cipher hoping that some alien fleets will come to end the Reaper menace once and for all.

"Looking at the massive amount of reapers that the fleet has, recruiting all the factions is still not enough and they don't have enough time to start building a powerful new fleet even using the best technology they had developed since the battle of the Citadel. My theory is that the Reapers have been doing the genocide cycle for more than one galaxy, a LOT of galaxies and maybe there are other cases where there is someone like Shepard trying to prevent them from coming back or that at least have some clues about this old machines existence.My idea is that there is a Reaper HQ somewhere hidden in darkspace where they have special relays that they use to jump to places like the Milk Way Citadel. Shepard would use the Citadel relay functionality to go to this HQ that is now empty because the fleet is travelling the old fashion way without using any relay jump. There he will send a message to every galaxy, with his knowledge that includes the prothean cipher hoping that some alien fleets will come to end the Reaper menace once and for all. "

I really hope they offer some kind of dlc pack that lets you play the game with pre-requisite settings from the previous games so I don't have to blow through 30 hours of ME1, and ME2 to load that character into ME3 to see alternate endings and scenarios based upon past experiences. Fuck that will take forever. So glad people you tubed the alternate actions and paragon stuff I just watched those vids instead of playing again lol. 

" I really hope they offer some kind of dlc pack that lets you play the game with pre-requisite settings from the previous games so I don't have to blow through 30 hours of ME1, and ME2 to load that character into ME3 to see alternate endings and scenarios based upon past experiences. Fuck that will take forever. So glad people you tubed the alternate actions and paragon stuff I just watched those vids instead of playing again lol.  "

" @137 said:

" I really hope they offer some kind of dlc pack that lets you play the game with pre-requisite settings from the previous games so I don't have to blow through 30 hours of ME1, and ME2 to load that character into ME3 to see alternate endings and scenarios based upon past experiences. Fuck that will take forever. So glad people you tubed the alternate actions and paragon stuff I just watched those vids instead of playing again lol.  "

if you have the PC version, you can just go on this website they had and download save files. "

" more recruiting? eh =/  wow i just noticed something.. i sucked at Mass Effect!     1. i killed Wrex 2.  Tali's exiled 3. Mordin's dead 4. Garrus's dead 5. Legion is dead   whats wrong with me? ;( "

Not 'Recruit the Factions', but 'Recruit the Shepards'.
 
Every single version of Shepard, Male or Female, Paragon or Renegade, is taken from multiple dimensions and fight the Reapers together as one giant army of badasses, while at the same time the Renegade Shepards argue over who is 'Shepard Prime' and the Paragon Shepards struggle to keep the Renegades from going too far.
 
Just kidding, that's a stupid idea. Seriously, though, it is pretty obvious that you're going to start convincing factions to fight alongside you as well as preventing any faction from messing up the anti-Reaper coalition for some stupid reason (the Rachni come to mind; it's highly likely the Krogan will be extremely unhappy to fight on the same side as they are at first).

ugh
 
if that is the case 
 
Renegade: Recruit only the pro-human faction or submissive aliens. 
Paragon: WE ARE ALL EQUAL! 
 
And then you fight the terminator baby again.

For some reason I just don't think allot of the smaller things will have physical effects, more a thing shown in the Mailbox like in the second game. I hope it's not that way though.
 
But as for the listed things go for me, Im gonna spoiler it all so...this is what I think will happen.
 

here is the question. those each race didn't make any effort to defeat reapers before under name of the whole united alliance? why Shepard? I know that the game is all about him or humanity. even though they will do it, it will be still hard to beat reapers. their number is too many. they are so powerful. they are literally big machines. organics have limitation, and disadvantage. reapers are literally weapons of mass destruction. of course, there is always something we can kill them. but that is just too ambiguous.