Well, if we talk on a combination of e.g. Eve and Starcraft, then i think of something like SWG which includes both space and planet bound questing/combat/pvp.
In addition, the original pre-CU/NGE version had a skill based system.
Finally, add to that sandbox. Player housing, etc.
Although, player housing alone is nice but not the same if not in a sandbox game. In EQ2 or LOTRO they don't really add anything to the MM part of MMO, as it does in SWG. Although, shops as in eq2 can make a difference.
So in the end *shrugs* we are just speculating wildly in all possible and impossible directions. And once we know, there will be the usual fanboys and haters......