It won't be Cyrodill; or at least not like it was in Oblivion. This is because they're not going to release the whole of it as DLC and since Bruma is the only northan city there isn't enough to just tack on the bottem of Skyrim. They could add loads of camps etc. and have Bruma as a northan capital either for/against the Thalmor (due to war) but it's unlikely and won't look like Oblivion due to the war and the 200 years that have passed. I haven't played Morrorwind, but I know it's big so we won't get all of it and I can only see it being used if it has major cities close to Skyrim's borders.
I also wouldn't wager it being in High Rock or Hammerfel because they'll be left for future games. Geographical I don't believe it will visit Valenwood or Elsweyr or Black Marsh (although Black Marsh would be awesome). A Daedric realm could happen, but we have already had Shivering Isles.
Some possibilities which I would like, would be something inbetween Skyrim's north and Atmora because they could use this a new land that hasn't been affected by the war. Or something like Blackreach that was under the WHOLE or Tamriel and linked you to vairious part of the world. For example it might reach a city in each homeland so you could see how each world has changed in 200 year. Not likely but I would buy it
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I also wouldn't wager it being in High Rock or Hammerfel because they'll be left for future games. Geographical I don't believe it will visit Valenwood or Elsweyr or Black Marsh (although Black Marsh would be awesome). A Daedric realm could happen, but we have already had Shivering Isles.
Some possibilities which I would like, would be something inbetween Skyrim's north and Atmora because they could use this a new land that hasn't been affected by the war. Or something like Blackreach that was under the WHOLE or Tamriel and linked you to vairious part of the world. For example it might reach a city in each homeland so you could see how each world has changed in 200 year. Not likely but I would buy it