To have some filler, why don't they have a crossover with Diablo? It can be purely non-canon, and the story will simply be that a wormhole rips in front of a location in Azeroth, where demons and cultists from the Diablo universe pour out, and when we enter, we basically play through Diablo 3's story. Content patches leading all the way to the final showdown with Diablo.
It'd be a great idea no?