It's probably been said 10,000 times but Skyrim online. Add in the maps from previous games, add dungeons/raids, chat channels, an AH, etc. and we're good to go. I really don't understand why they felt the need to recreate the game using a formula that WILL NOT WORK. With Skyrim they have a unique and interesting gameplay style; just incorporate basic MMO features into it and you have a really good game that has the potential to attract MMO and FPS-minded players. Just for a little example, I have friends that swear by CoD and wouldn't dream of touching an MMO like World of Warcraft. These SAME people also have Skyrim (for console) and have invested HUNDREDS of hours into it. I'm sure these people would buy a Skyrim online.
With the original game formula they have potential to make a very successful MMO that attracts more than MMO players. This is what TESO SHOULD (but won't) be.