I don't know why but I'm convinced we're getting Kul Tiras as the new continent. Possibly because it's being really pushed on with the PTR datamining and Blizzcon key art, also like some here pointed out the map very much looks like it can hold multiple zones. Size/scale doesn't seem it's much of a problem (look at Tol Barad and Broken Isles)
I'm still not sure if if it's a good thing or not. Would you rather have Kul Tiras as an island-continent or a zone together with other islands?
I think, for now, the former is better. Look at how much new lore Broken Isles 2.0. brought. I definitely would like to see Zandalar and Kezan as leveling island-continents as well in their own respective expansions.