He was the leader for all of 20 minutes.
Which I still want re-implemented back into the game, dangit, that was a good scenario. They referenced it in BFA, and players who didn't experience it must've been confused.
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My money is on either permadeath or ironic punishment of her soul, with Horde and Alliance forces lead by either the forsaken or night elves depending on faction being present for the raid encounter. At which point they take her corpse and either drain that banshee blood to go sign that peace treaty or eat her brains.
The two factions have both been given reasons to want her dead, and I expect it to be the factions that get to canonically finish her off. That's just straightforward storytelling, like Velen and Illidan being present when we defeated Kil'jaeden.