As you may know already we are going to Argus... in some near point of the Xpac, HQ of the legion, and where supposedly the army of light is fighting against the burning legion..
So.. Turaylon sends a message about the status of the fight and they need our help, but what if the message also went into another AUs, the AU Draenor for example, where we defeated the legion, stopped the orc invasion to AU Azeroth, with that in mind and that Nerzhul never became LK, that AU Arthas got his full training becoming a Paladin fighting the demons and the scourge, never corrupted following only light, stronger than tirion or Uther, so this AU azeroth answer to the call of fighting the legion in Argus, as well as the Draenei and Orcs from AU Draenor?
Yeah sounds crazy, but.. with the New LK plotting and making weird things in Northrend.., this would be badass and see the full potential for an Older and Wiser Paladin arthas, along Muradin and Uther as a Team.
Just an opinion, or theory but hey WoD happened! xD