GDC 09 was the perfect time for Infinity Ward to take the shroud of secrecy of its upcoming Call of Duty: Modern Warfare sequel. It would have been the perfect time to announce and show of the game's co-op gameplay modes. Unfortunately we are only left with a teaser trailer that doesn't really show us much of anything except a release date.
11-10-09
We really aren't any further along than before, and it's still unclear as to whether or not the latest CoD will support co-op, but if the community feedback is any indication - it damn well better have it!
Source: Modernwarfare2.infinityward.com