The current wielder: http://www.wowpedia.org/Tirion
What it is: http://www.wowpedia.org/Ashbringer
I would presume such a powerful item isn't going to be given to the Alliance or Horde when Tirion finally croaks. Do you think we'll see it be used again in the lore or have it be kept within the Argent Crusade's hands? ( Spoiler: Tirion is old. ) I don't see it returning to surface unless we got another Scourge-themed expac.