So I was thinking about Wrathion, and eventually the thought process led to a video:
Essentially it's a history of Wrathion, why I like him, and a theory I figure would be interesting to discuss while we sit here doing nothing during maintenance.
Essentially, the core of the theory comes down to the fact that Wrathion seemingly will do whatever it takes to stop the Legion, combined with his grey morality, and his fascination with the Titans. Basically, once we finish the Siege of Orgrimmar, Wrathion is going to reveal that his ultimate plan, which he hints at in the end of the new 5.3 legendary chain but never actually explains, is to bring the Burning Legion to Azeroth purposefully. He is going to open up portals to the Twisting Nether and start the next invasion of Azeroth personally.
Because what better way to bring the Titans -- a group Wrathion has become increasingly-fanatical about -- back to Azeroth then to bring back the faction led by their former champion. In addition to this, the obvious chaos of the Legion's return would give the Old Gods another chance to move to try and reclaim the planet.