The key draws to playing an mmo are a social atmosphere and persistent world. This results in difficulty playing for short times or stepping away easily, and an ever growing barrier of entry for new or returning players. Wow addressed these with piles of easy wqs and instanced pugs + complete mudflation each content push, and is successful for it, but does miss a lot of people who like a social world community or long term character buildup. They will probably get a lot of return subs with classic wow for this reason, we will see if they stick around long or not.
In the meantime, mmos largely seem pretty weak on utilizing modders for content, browser or mobile use, or even consoles. The ones that do have flaws elsewhere. Meanwhile, the expected use is stuck really high: an rpg can be a raved about hit if you enjoy 100 hours playing it, while an mmorpg that only sees 100 hours played is probably a heavily criticized flop.
Mmos will do fine when one come alongs that doesn't try too much reinvention. A few gimmicks maybe, but largely that classic mmo feel including grinds. New graphics, web or mobile access, stuff to do for short play, and by some miracle able to balance the community draw with letting people log out when they have to. PokeMMOn or The Wire Online or World of Starcraft, who knows.