So, anyone who has played Killzone 1 and 2 know that the Helghast wear there masks because of the atmosphere and that they have started to change physically and all that.  Well, in the new trailer it shows (in CG) a soldier fighting several Helghast in melee combat.  This could be to show off all the new moves, or it could just be a trailer with no real purpose other than being a teaser before E3.  I thought something interesting though is at the end when the soldier looks at the camera and puts a Helghast helmet on.  This got me thinking...what if "we", the soldiers from Earth, have been on Helghast so long in the war that they are now needing to use the same breathing equipment and not becoming quite so different from the Helghast after all?  This could be just a trailer with no meaning at all, but I definitely found it interesting.
 
Also, I hope Rico dies violently at the beginning of the game.  He is one of the worst characters in modern gaming.
 
Link to trailer:  
http://kotaku.com/5554541/the-first-killzone-3-trailer-is-a-real-kick-in-the-face

The thing is the Helghast changed over years and years so I dont see how Sev and co could change over a few weeks. Most of the Helghast soldiers probably shouldnt even wear the masks because their on Helghan anyway. I hope that melee isnt the  big thing they are trying to add to Killzone 3 because it doesn't look that good. 
 
@sammo21 said:

  Also, I hope Rico dies violently at the beginning of the game.  He is one of the worst characters in modern gaming. 

Well, do we know how long the 3rd game takes place?  The Helghans have done a lot to their planet in the way of nuclear stuff, so who knows.  I just found it interesting, unless maybe there are levels where you disguise yourself, and others maybe, as Helghans in a few levels.
 
I also hope there is a co-op option.

" Also, I hope Rico dies violently at the beginning of the game.  He is one of the worst characters in modern gaming. "

I don't think it was CG.  I think it's in-game assets cleaned up and ran through a stylized filter.
I took the helmet thing to mean undercover missions.  And yeah, I think everyone wants Rico to violently die as soon as possible - they will have to do a lot to turn his character around otherwise.