In the End of Time dungeon, we got a view of what might happen to Baine. The description of the fight says:
"Enraged by his failure to protect the world and, most importantly, the Horde, this time-ravaged shade of Baine Bloodhoof lingers within the ruins of the Obsidian Dragonshrine. Although he's still as powerful as the tauren high chieftain from the present, within this shattered future Azeroth, this guilt-ridden echo is little more than a discordant vessel of unquenchable malice and anger."