Most MMO's wouldn't be very playable with a controller. Maybe if Microsoft allowed for proper M&K support next gen it could happen. But I doubt it.
Not only that, but MMO environments are not very friendly with fixed hardware. Developers never know how many people may be in a particular zone or just what may be going on at a given time and this is going to have serious performance implications. And if they try to compensate by severely limiting the number of players in a given area (instancing) it's just going to end up dumbing the game down and hurting gameplay.
I can see the problems with hardware limiting what could be done with a mmo on the 360. Starwars much like DC universe online is very much action oriented and dcuo works perfectly fine on the ps3 dispite a little menu lag. I've had no problems the way the controls are mapped to the controller.
I wouldn't think it would be that hard to get something similar running on the 360 or if it's too late in the 360's hardware then start planning on the next gen version.
There is such a untapped market out there for this. I mean if the try and cram a rts game onto consoles with Gimped controls you would think by now someone would have tried by now with a mmo.
And yes I know the final fantasy mmo is out there. I personally don't count it since it's a 7+ year old game with a horrible interface and controls even on the pc.
Hell even the dreamcast had phantasy star... While not being a true mmo is closer than what we have get these days.
Sad that the closest we have seen on the 360 recently is a indie avatar game that is a mmo but unfinished and possibly the ugliest thing I've ever seen... Yet people play it lol
'Happy is he that taketh Thy little ones and dasheth their heads against the stones." Albert H. Fish "GrayMan" Serial killer and Cannibal