User blog comment:Atvelonis/E3 2018 Coverage and TES VI Teaser/@comment-1600847-20180611203626/@comment-1600847-20180611225044

Based on this pic https://i.neoseeker.com/u/a/12/mappagigante.jpg, I'd say High Rock is about half the size of Hammerfell. I can see them making a game set in both.