Meh. I'd prefer a new IP if Bethesda is making an MMO. The Fallout universe is okay, but I didn't like the rather small selection of weapons available in F3 (although the custom ones were awesome, Railway Rifle ftw). TES has always been about the "One Hero" and I just don't see it working very well as an MMO, especially with the threat from Oblivion recently vanquished. An Akaviri invasion or something could work, what with the Nerevarine having gone there and all, pick a faction and stuff, though Akavir has long been a continent at war with itself, unlike Tamriel. But I'd still prefer a new, solid singleplayer TES.
All of my personal opinion doesn't mean I won't buy anything they produce anyway, though.