I know this pretty much ended any speculation of Mannoroth, or even that Gul'dan would get Grom to drink the blood after all.
Really IMO this seems to cast a ton of doubt on the entire idea that the Legion would usurp the storyline at the very end. They just got beaten in a big way by the Iron Horde, doubtful they'd send somebody as high profile as Archimonde in right away to fight the Iron Horde, the Alliance, AND the Horde.
So really, we're kinda back to square one on this whole deal. No clear cut ending Boss.