Disclaimer: I’m not a Wrathduin shipper, I’m just looking at the facts.
Christie Golden, the woman that started it all (she wrote Wrathion and Anduin’s friendship in War Crimes) is writing Before the Storm, we all know that it’s supposed to give development for a ton of characters in the game, with Anduin and Sylvanas in the front.
WoW is slowly becoming more progressive (female warchief, fat humans) and the final step they have to do is broadcast a major LGBT relationship.
Most of us know Anduin is probably gay or at least bisexual. So if and when Wrathion all of a sudden comes back to apologize for all the shit he’s done, Anduin will realize that his friendly feelings aren’t so friendly after all.
It at least makes more sense then sending him off with Jaina or Calia, both of which he has never met or talked to. Tess would make sense but I’m not sure that Genn, proud bastard that he is, would want to give away his entire kingdom like that.