Its possible to play any game in the rift right now.
The current MMO's wouldnt be very good tho with that type of experience.
They would have to be more streamlined like a FPS to be any fun in VR. Definitely possible, just would need a new way to play MMOs.
I know 2nd Life has full Rift support right now, but haven't tried it.
One thing I think is outdated thinking on the current Rift, is the way we view the screen. It's very immersive, but there is got to be a way to do it better.
Currently its a set of lenses looking at a screen.These guys are trying something diffrent.
After being in the rift for a couple of days, I am now in full support of VR. So I'm looking to fund any of these projects.
The way we view entertainment is outdated.