You forgot 5. We have to deal for sylvanas simps for a lot longer than anticipated :/You know what's the dumbest thing about all of this? That it's obvious what will happen next:
1. We won't kill Sylvanas, because she knows the Jailer's plans and that's an advantage we cannot afford to dismiss.
2. Wherever we go next, Sylvanas will come with us and she'll be a very, very important part of that story, but this time on our side.
3. With her soul restored, she'll experience a lot of remorse and other feelings that she hasn't felt in years, so that we can feel bad for her.
4. At the end of the next patch she'll do something to save Anduin - if she sacrifices herself by doing so, it will turn out that having Anduin back was the key to stopping the Jailer, if she doesn't then she'll also help us defeat Zovaal. Either way, that will complete her redemption arc.
The only remaining question is what will happen to her in the end? I hope that if Blizzard doesn't kill her off, she'll just stay in the Shadowlands.