Vulpera and Lightborn Forsaken for the Horde
Sethrak and Mecha Gnomes for the Alliance
I also think Calia replaces Sylvanas as the leader of all Forsaken and becomes one of the leaders of the Horde. Her along with Baine, Saurfang, the return of Thrall, and the head Nightborn chick lead the way for a meaningful peace treaty, which allows Blizzard to have an ‘in’ for cross faction grouping for endgame content.