They won't redeem Sylvanas, and before anyone mentions Kerrigan:
1) Kerrigan was actually the player character for 1/3 of Starcraft franchise, so of course they want to satisfy the player and make them win. Sylvanas is an antagonist.
2) Kerrigan was mind-controlled by Amon when she slaughtered trillions while Sylvanas has free-will.