I really can't wait to see the improvements in Killzone 3, I think the varied mission types in the multiplayer made for a very interesting experience and I would love to see that expanded upon.  Maybe more varied types of assassination, where it doesnt end after one kill, but the amount of specific kills a team can make determines the winner.  The unique mix and match class based system really held my interest for the months that I played it.  One of the few things I feel Guerrilla must improve upon is the amount of levels one can attain in classes and overall, I quickly hit the cap and had very little left to do in Killzone 2.  With some more levels/unlocks they could greatly extend the life of their multiplayer.

Oh, and let me kill Rico for the single player. Please.