On a recent episode of GameTrailers TV, Jack Tretton has opened up on a little confirmation that the infamous Guerrilla studios game, Killzone 3, is in the works.
Talking with GameTrailers, Tretton said, "Well, we own Guerrilla Studios and they did a great job on Killzone 1 and 2. I don't know whether you'll see announcements about it [at E3], but I can promise you a Killzone 3."
So there is confirmation that there will be at least a trilogy to the ever growing Killzone series. Even though it may not be out for a while, it will be interesting to see what they do with multiplayer, especially since some of the major FPS releases of this past year.