I think that it would be a bad idea for Bethesda to go mmo. I don't feel that the mmo scene is up to the quality standards that I have for an Elder Scrolls game. I put Elder Scrolls games above mmo's in the list of quality rpg games.
!dea:
I think they should go multiplayer, but somehting more along the lines of Borderlands. Some sandbox world with about four player coop, and then add a separate multiplayer vs mode.
vision:
The Elder Scrolls worlds are already so robust and life like that I would really only want to play with about three to five other players at the same time. It would be nice to have been able to run around Morrow Wind/Skyrim with my friends, questing and looting. I would like to see a system of social interaction implemented instead of scripting the whole thing. Some type of content delivery system, that would offer quests from a pool of content from anyone how you interacted with. Hard to describe but I can see it in my head.