The Horde are the underdogs here where they weren't in MOP, that's a huge hint at who the aggressors are in BFA. I don't know what drugs you people are on that are actually expecting Sylvannas to go all Garrosh but you should stop smoking them.
It should be really super obvious otherwise that any xpac that's sort of in the vein of MOP would not feature Horde being the "bad guys" again.