When Microsoft announced Halo 4 last year at e3, and didn't show any actual in-game footage, I personally felt like it was all a ruse. Sure, they are working on Halo 4, and they would love to get it out this November, but here we are, and it's almost February, and yet we still haven't seen any in-game screenshots or video footage of a game that is supposedly coming out this year. Seems a bit suspect to me.
Look at GTA 5. There is no guarantee that GTA 5 is a 2012 game, yet we've already seen some in-game footage.
Certainly, MS might show something at GDC, but man... I just think that if this game really does come out this year, the single player campaign will probably be as short as a Call of Duty game. I'm just getting the feeling that if this game is really coming out this year, it will be a rushed product.