So lets just call it out now. Everything sylvanas has done, since her death after jumping off icecrown, has been to reach this moment. In the story she know when she fell and died from falling from icecrown, she saw her what awaited her, an eternity of suffering for her state of being.
And since then, all she has been doing is an attempt to stave off her own death and face this end.
The forsaken, the horde, the war, she stopped giving a dam about that, as she said 'the horde is nothing' at the end of the saurfang cinematic, she hasn't given a dam about any of this, only using everyone for her own single goal.
And this is what its all lead to, her controlling death itself, so she can avoid that end she feared so much.
This is where you realize, this is as good as it will ever get for her, and if you just think about the progression of this story, you know this is where she'll die, and probably worse then death, since she's just screwed over death itself.
so yeah, i would say sticking being a loyalist to her might be bit of a sad outcome.