Considering that a logical Sargeras fight would be for a raid of level 100 adventurers, and the fact that the new expansions as of late have been raising the cap by five levels, it is very possible that there would be a level 95 expansion before we go on to Burning Legion (besides, Blizzard would want to keep people playing WoW at least until project Titan is officially announced in a few years). Another reason supporting this is that we still have the Emerald Nightmare plot line to explore. It would also make for a very good new 'continent' as well.
Your thoughts?