up and coming
Keen and Graev have a post, which Tobold has responded to, on an article up at Yahoo which tries to guess what the next big MMORPG will be. If you are currently not up to snuff on who the up-and-comers are, reading these will get you a long way there.
Weighing in on the topic itself, there are a number of good features that certain games have created that haven't been all rolled into a new game. The current batch don't seem to be doing it either - Lord of the Rings is perhaps the closest, and they don't seem to have the right ideas to move forward - I think they may be too focused on WoW as a model. Too many of the others seem to be ignoring the fact that people enjoy doing things other than killing in-game. Really simple things like fashion and player housing have been ignored for far too long. See Tobold's post responding to Trinity for more on this subject.