I'd love to see a FPS-RPG merger (like Fallout3) thats MMORPG also. I think that would potentially be a cool game, as well as "stretching" the engine in all the directions I want it to go.
well if we want the engine stretched lets hope it's a 2d/3d mmo-fps-rpg-rts-tbs-vehicle-puzzle-action-adventure game.