This is a mis-interpretation: Sylvanas always had free will. The Issues with her were that she didn’t have a soul and also ~for whatever stupid reason~ thought that a guy called the jailer who clearly wants control over everything would somehow free everyone.
Also the narrative as I understand it is that she’s been in kahoots with the jailer since Wrath.
I mean… the character that we’ve known for the past 22 years is dead. The meat sack that is called Sylvanas still exists.
I’m skeptical their are any plans on bringing her back.