I don't think anybody's said it and I was just thinking about it.
 
But if your Shepard didn't make it couldn't that marine with the sniper have been the new character players would take control of? 
 
I'm just speculating but judging from the leaked EA pre-order screen for Mass Effect 3, couldn't the game start with Earth getting destroyed and if you don't have Shepard you start off on Earth surviving the attack. 
 
Kind of like how you picked how Shepard's background was in the first game, you would dictate the character's backstory on what you do in the first hour or so of gameplay. 
 
EDIT: Nevermind...

I thought Bioware said that if Shepherd dies in your game you won't be able to carry that save over.

The death storyline isn't canon.
 
Which really makes me dislike ME2 even more thamn I did already. I mean, the big thing for ME2 was "OH SHIT YO, YOU CAN DIE AND IT WILL MAYBE POSSIBLY EFFECT THE STORY WINK WINK NUDGE NUDGE"

I feel like I've destroyed a young boy's dream.

"The death storyline isn't canon.  Which really makes me dislike ME2 even more thamn I did already. I mean, the big thing for ME2 was "OH SHIT YO, YOU CAN DIE AND IT WILL MAYBE POSSIBLY EFFECT THE STORY WINK WINK NUDGE NUDGE" "

" @Three0neFive said:

"The death storyline isn't canon.  Which really makes me dislike ME2 even more thamn I did already. I mean, the big thing for ME2 was "OH SHIT YO, YOU CAN DIE AND IT WILL MAYBE POSSIBLY EFFECT THE STORY WINK WINK NUDGE NUDGE" "

If some of party dies then that DOES carry over into ME3.  If Shepard dies then that's end of the story right there, can't have the ME trilogy without Shepard. :)  "

Developers have been known to lie about stuff in their games before.  So there's the possibility that the character you see may be the one you control. 
 
This is pure speculation though, and a lot of it.  Face it, that'd be the perfect point in the series where you'd go, "Oh shit!"

" Developers have been known to lie about stuff in their games before.  So there's the possibility that the character you see may be the one you control.  This is pure speculation though, and a lot of it.  Face it, that'd be the perfect point in the series where you'd go, "Oh shit!" "

I dont think you will play as that Marine but i think its possible he could end up as a party member.

Heh, I thought this title was going to be an ironic jab and how bioware has introduced yet another shave-headed buff male that looks the same as every other version of that archetype. Also, you're idea is way better than what they'll end up doing. 

You can play as 'That Marine' in Crysis: Warhead if you really want to.  Cor blimey, Guv'nor!  Aliens!
 

" I thought you were going to say he would be one of the companion characters well...I think he might be "