FPS? That makes sense to me. Given the company involved and the wonderfully violent nature of the 40k universe. Unfortunately, MMOFPS games aren't really my cup of tea and tend not to stay in the market for long.
RTS? Given the success of Dawn of War and its expansions and the nature of the actual tabletop game, I can see a company trying to crank out some strange MMORTS sort of thing. How would that work? Hell if I know.
RPG? I just can't see it. Okay, presume that everything is restricted to a single planet. Now, restrict everything to a certain span in the timeline. Remove vehicles (make them unpilotable, just terrain), limit races, and maybe you've got something that they can actually develop but I can't see it selling in that form.