Yes, it's likely that such an expansion will include Kul Tiras, the naga, and N'zoth, but the idea that we're going to island hop around the Great Sea and/or South Sea is nothing more than fan-fic/headcanon. Zandalar and Kezan are too important to be relegated to minor zones, and as it relates to WoW, the "current" scale of the area doesn't matter, e.g. see the lore behind Stanglethorn.