Look at the World map.

The south could be Land of Madman, the west the Seanchan, the east Shara and the north the Westlands (Or maybe some civilization up on the Northern icecap?)

Unlikely. How would they be as one? We never heard of the Land of Madmen in the books, and Seanchan and Shara we don't see a lot (not at all for Shara) so it would be weird to have a major prophecy we can't expect. We have the Westlands split into two, somehow like the cold war, and two major rulers, and that prophecy would refer to obscure land we only gather rumors of?