Possible Outcome That Could Salvage Sylvanas and Give Some Night Elf Reparations
Chances are Sylvanas would realize she is being played, all along, manipulated by smarter more intelligent and malevolent beings that used her fears against her.
She would then do something very intelligent and heroic, like possibly trap Azshara or N’zoth in Xal’atath saving us all. She would lose the warchief position for her actions especially the war, but everyone would realise the whole war of thorns and horde war was because of manipulation of Azshara and/or N’zoth, but despite the great harm Sylvanas did, she is also the reason the world survives far greater calamity.
Made more poignant if she ends up also being the reason Tyrande and the night elf people survive Azshara (or Tyrnade gets to finish of Azshara or beat her in a future encounter, blizzard woudl have to play this right, cos people would hate Tyrande agian having to be rescued like a damsel in distress, so it would have to be somehting Sylvanas does that gives Tyrande the edge over Azshara or allows Tyrande to be able to turn the tide and together they finish the Queen) and also the reason night elves possibly get somethign amazing like Zin’azshari and/or naga elf sub-race joining them in addition to their kalimdor lands and the borken isles including some working relationship with the nightborne despite being in opposite facitons. [this would be part of Sylvanas making amends]
Sylvanas will then now be a free agent. Calia would lead the forsaken, Thrall the horde and Sylvanas would be a major character roaming the world rediscovering her original self, and be a hero working to do the best she can as she becomes her old self in the curse of undeath. Maybe in that there would be role for Delaryn and Sira tood, and we have a cadre of elven hunter undead babes meting out justice in the world
She might get a new model too to reflect this.