Sony Computer Entertainment have stated at the Games Convention in Leizpig that their upcoming FPS, KILLZONE 2, will indeed have bots for the online multiplayer. The bots will be fully customizable difficulty-wise, and players can use them online or offline.
Vehicles will only be available in the single-player mode when you buy the game. Guerrilla will be patching the game after launch to include vehicles in online mode. That patch will also add a cooperative mode for the story. It is quite surprising that this isn’t included all on the disc, considering the delays the game has faced.