Do you think there will be a system similar to Civ 6, where the world is "round" in the combined map?
In Civ 6 if you look at the minimap you can go west and west and when you are at the end of the Minimap you´ll simply end up at the other side.
This applies for the game and the units.
For a world map in Warhammer this might be a good addition and could get rid of the coners.
E.G. Play Dark Elves and than send one army West to Ind, and the other one east to the old world for pillage and plunder.