Aw, no. Not MMOs. Haven't we already had enough of this? Didn't anyone learn anything from FFXIV?
Alright, gut reaction aside, I have a few things to say. As long as they're still making TES:V, I'm happy. And, thinking back to Oblivion, that is one of the few games I can imagine working as an MMO, but the key thing here is that they can't just copy WoW. They would have to do something completely new and different from anything that's been tried before.
Some suggestions for what they should try: (Warning! Wall o'text ahead!)
1. Maintain the option of first person perspective. Give people the sense that they're still playing in their own game, and break away from the standard MMO interface. Anything they can do gameplay wise to distinguish it from WoW will give it immediate bonus points and help it stand out.
2. Try to make it work as a console MMO. This isn't new. It's not like the capacity to share a game world across Xbox Live or PSN doesn't exist, even if it will be expensive. Break some ground there, if possible. Technology is only getting better, right?
3. Borrow some aspects from text-based MUDs. Iron Realms has been going on for ages. Use some of what makes it successful. In-character roleplaying, for starters. Let players advance through the ranks and become important or influential within the world, if that appeals to them, and create a world that relies strongly on both teamwork and conflict between player clans/cities/guilds/races/classes etc. Give it an ever present yet fluid story that the players are a real part of. Have one nation always be at war with another. Let people choose to be good or evil, etc, and make sure they always have something worth fighting for, or worth fighting against.
4. Polish it! Don't make the same mistakes FFXIV did. If there's any aspect in this MMO that wouldn't fly in a single player game, fix it. Make monsters and characters have realistic fight animations so that a battle looks like a battle. Animate enemies so they react to being hit. Create tension and drama so every fight feels like it could really kill your character.
5. Allow every character to look distinct. Too many MMOs have identical clones walking around, and I know that has a lot to do with limitations of rendering and all that, but, seriously, with a character creation screen as flexible and well made as the one in Oblivion, people are going to be expecting that. The variety of races is already a point in its favour. (more so, if including different subspecies of, say, the Khajiit).
6. Give people an incentive to keep playing. Questing is the obvious one, but, clearly, they aren't going to be able to constantly keep writing new quests all the time, so create a benefit to keep people playing. Let them live in the world. Give them an incentive to, say, own a home in a village, and take on a profession, such as a craftsman, a city guard (see above, re: inter-city/international conflict), or even pursue politics and vote on issues that affect the game world, like policies that would impact the local economy. Reward guild members for teaching new players about the game and their class skills. Again, Iron Realms does this brilliantly.
I'm sure other people have their own ideas, many of them far better than mine, but, anyway, those are the first few suggestions that came to my mind. Chances are, it will just be a WoW clone, though. Or, if TOR proves to be successful, then a Fantasy-skinned version of that.
If anyone can think of anything else that needs to be done to correct the mistakes that make most new MMOs fail, or can see a painfully obvious flaw with any of the suggestions I've made, then please respond. I find this interesting, and I think the gaming industry's obsession with trying to compete with WoW is something we really do need to have some discussions about.
But, anyway, all I'm holding out for is the single player TESV.