Hold the phone. It seems that Space Marine will be getting a game mode called ‘Exterminatus’ within it. This is a four player cooperative game where, at least from the screen shots, players take on hordes of Orks.
But don’t grease your palms just yet. According to this article released 3 hours ago on Gamespy, this game mode won’t ship until October in a DLC package. This is perfect given that most people should be finishing the single player about that time anyway. To casually keep up to date on Space Marine, check out their Facebook page.