Personally I'd really like to see another game set in the Three Houses universe, but focusing on one of the areas outside Fódlan (Albinea, Almyra, Brigid, Dagda, Duscur, Morfis, and Sreng being the options here). I think that a game set in Dagda would be interesting, considering that it got damaged pretty badly during its most recent war with Adrestia and I'd like to see the long-term consequences of such a devastating loss.