It's unlikely that will happen given they would have to replace all npc's. Worst blizzard seems to do is destroy the cities.
Though it is strange how blood elves are cozying up to the highborne and Suramar. It doesnt seem out of the question, but it would be unprecedented for a faction to take over a major city of the other.
Would you trade Silvermoon for a Suramar properly fleshed out as a player city?