I disagree wholeheartedly about not seeing the rest of Skyrim. Not for all of Skyrim, but for one hold in particular: Winterhold.

In TESV, Winterhold was in ruins due to the game taking place after the Great Collapse, aside from the College of Winterhold. Since the Great Collapse happened in the Fourth Era and ESO takes place in the Second Era, Winterhold is still standing in ESO. And personally, not only do I think it would be interesting to see what Winterhold was like in its former glory, but it would pretty much be the only time we'd get to see Winterhold in its former glory.

Other areas I'd personally wanna see include Taneth, Blackwood, Western Black Marsh, Eastern Morrowind, and Pyandonea.