My idea would be that in a future expansion that involves Bolvars death and the vacuum for a new Jailor that Sylvanas becomes Lich Queen and pits the Scourge against the Void which is why they fear her because of her newfound power. The purpose of the Lich King in the new retcon was to turn everyone Undead and safeguard Azeroth after killing G’huun. As Lich Queen Sylvanas would be entirely neutral and remain an Anti Hero. That way it pleases those who don’t want her killed off and the ones who wish her not to be Warchief.
Or she can just stay as Warchief and prove to everyone that she is right about ‘forgetting what makes us strong’ (Conflict); The Pandaren said the same thing.