Not a MMO but if you have taste you're looking forward to this title. I still have more fond memories of Fallout 1 and 2 than I do of my first girlfriend. CVG has an interview up with Bethesda regarding their upcoming game.
You may want to start with Part 1.
CVG: Do you see the rise in popularity of the MMO genre having negative impact on the popularity of single-player RPGs?
Hines: Not really, because if you look at the kinds of things you can do in an MMO - and I've probably spent 250 or so hours in World of Warcraft - the kinds of things you can do in World of Warcraft are really very different than anything you can do in Oblivion.
MMOs have a much more difficult time creating a sense of permanence. You can't let one person do something that nobody else in the world can do. Every quest that you do... that thing 30 seconds later has to reset itself for the guy coming behind you who also has that quest.
Whereas in Oblivion, whatever you do is done. The whole world is meant to focus around the experience of only one character, and everything in the world that happens revolves around that one character.
In Oblivion, if you're playing on the PC and you want to give yourself some completely game-unbalancing ability or weapon or whatever, who cares? It's your game, you're not affecting anyone else's experience. But in an MMO, everything has to be very balanced, that everything you do has to be set against "Well, what can everybody else in the world do?"