Shivering Isle for the CHEESE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Shivering Isle cheese is just to die for.... mainly the guy next to you then you can use his end trails as a skip rope.
The Reach/Markarth- Independent Reachmen kingdom hell yeah.
Thras- Not holding out hope for this one, but it would be so cool, and I know the writing team has a few Sload fans. Pyandonea would be awesome as well.
Alinor- Or anywhere on mainland Summerset provided it looks 80x cooler than Auridon.
Shivering isle for sure, this would be an excellent zone to have in ESO, in all its glory mania and dementia.
Collage of winterhold is a big one for me also, with a room to yourself maybe with a bit of customization ( like skyrim)
And different classes demonstrating magic use ( for the atmos and immersion).
Anywhere I haven't seen before in a modernish game (Morrowind onward). Preferably a non-human region. My first choice, Valenwood, is already done, so now I'd like more Elsweyr.
I'd like to see more Elsweyr and more Hammerfell. Out of the things we know are in development, I think I'm most interested in seeing the Spiral Skein (Mephala's realm). I hope it's a full zone like Coldharbour and not just snippets of the realm like we had with Shivering Isles in the Mages Guild quests.
I want to see the daedric realms we haven't seen before, as well as see some of the areas change as the time 'progresses'. Watching Windhelm become more and more similar to the Skyrim version, and same with Morrowind.