Keep in mind what they've said about DLC size. They said "Big" as in Fallout-3 style. Point Lookout was the biggest DLC for Fallout 3, but was still smaller than Shivering Isles IIRC (it's been a while since I went through them). They aren't going to try and fit an entire province into something roughly the same size. They can still do a lot, which is why I think an island expansion, elongated questline, Daedric realm, or Orsinium (props to whoever first suggested that in this thread) is what we'll end up with.
Nova Orsinium, is an Orcish city province located within Tamriel. It featured prominently in the The Elder Scrolls II: Daggerfall as the Orcish capital city.
Got that from elder scrolls wiki.
If it has already been featured in Elder Scrolls Daggerfall, then that's kind of the same concept, of a game played in the past. So, if your saying to add Orsinium, then why not Morrowind? Both were featured. What makes Morrowind a better choice, is that it's viewable, and confirmed to be there. All that needs to happen, is open those 2 gates... I hope!