If they do the same "split soul" thing as with Uther, it will be kinda meh. It works fine with just one character (and that already is Uther, his story just happens earlier in SL), but after that it'll just be repetitive/overused and virtually lifting a portion of responsibility from Sylvanas. Still, I kinda stopped caring much about her plot after 8.2.5, so let's just brush her off the story somehow idk. The Jailer/Anduin stuff is fine, SL are fine, Sylvanas I just don't really get anymore.
Next to return and be redeemed. Arthas.
I can definitely see a quest in 9.1.5/9.2 where we encounter some spirit roaming the Maw that looks like Sylvanas. We manage to speak to it and and get this monologue of;"I am Sylvanas Windrunner, or at least I was, but I was never the Banshee Queen. My final moments were not atop the tower of Torghast but amongst the trees of Quel'Thalas, facing down the Scourge hordes that were ravaging my homeland. I know that Azeroth has suffered greatly at the hands of the Banshee but that dark reflection is at last no more and I may rest."Then she fades into anima and we get some memento/toy.
So literally none of Sylvanas' characterization, from the point in which she first appears in Warcraft 3, until now, simply does not count. I have to hand it to the writers for giving Sylvanas an arc both people who like & hate her, will absolutely hate.
My favourite thing about this topic is how reasonable and respectful everyone always stays! No-one ever makes strawmen arguments or weird ad hominem attacks! <3
Garrosh was completely in control of his actions after Seige of Orgrimmar, so no, Garrosh is still objectively bad. He deserves revendreth much like kael'thas, but I don't know why you guys want everyone to be redeemed. Garrosh will go through revendreth and that will be his fate, and Arthas, we don't know too much there yet, but again, he's part of the shadowlands now so he will likely be thrown into one of the places.Sylvanas is a bit different since she hasn't "died" died yet like Arthas or Garrosh, but even if they do "redeem" her, the best way to do it is to just have her soul be freed/merged together and she is judged based on her life before undeath, or she kind of explodes anima wise like Nerzhul and has a similar moment like he did referring to Rulkan.
Everything else aside.. This is neither a folk nor a fairy tale..
I think - credit to Matt Rossi - that a "redeemed" Sylvanus having to deal with the crushing agony of what her evil twin did would be a worthwhile arc. I wouldn't call that soul-crushing load redemption by any stretch. The guiltless redemption discussed in other posts just completely reduces her to a victim and she is too good a character for the writers to give her that fate. She is too proud - elf or banshee - to accept that premise.