Well, some random thoughts here: Sylvanas tried to enslave Eyir but failed. She's desperate to secure her immortality. Meanwhile, the new Lich King seems to be planning something.
Do you think Sylvanas will look for deal with the Lich King?
While Sylvanas hated Arthas, that was a personal quest for vengeance. In her short story, she finds out that someone else became a new Lich King and couldn't care less about it. With her future hanging in the balance, would she submit to Bolvar?
We know Legion is setting up plots for future expansions. Among all the Void talk, we also have a few hooks for Lich King and the huge Sylvanas/Genn conflict in Stormheim that looks like won't be solved during Legion. In addition, Alleria's return and Vereesa's words in the Vindicaar indicate that we may deal with Sylvanas again soon.
So, what do you think?