So, im not trying to especulate much about how the story will go, who kills who and so... But from a merchandising point of view, Blizz would want to show in game all the characters that would appear in the movie, so traveling at some point to AU Azeroth would be a way to do this.
As we allready are in an alternate universe, and the movie comes out in july next year, we can asume that hellfire would be ocming out around june-july. With a 6.3 in december, 6.4 with the movie and a new xpac in december.
Just saying, if they want to sell a game related to the movie, it must be WoD 6.4.