I guess, but that ship has already sailed with Before the Storm. Humans get to see forsaken as individuals and embrace them, heck, even Gen comes to that realization.
The night elf problem? As in Night elves not accepting forsaken into the alliance's ranks because of Teldrassil? The Desolate council were killed prior to that and had no responsibility in it, and we don't know if Calia would make up a race of defecting forsaken, or raise new ones. (New ones wouldn't trigger night elves since they would not have been responsible for teldrassil either). Or maybe I'm misinterpreting what you meant, I apologize if I am!
- - - Updated - - -
Forsaken defecting because of Sylvanas denying free will to Derek is a reasonable idea. It's their most fundamental tenet as a race.
Regarding setup and hints towards it, I will agree that there haven't been many. But the Desolate Council's tombs in Arathi, and Jaina asking about Calia are exciting small things that give me hope
Jaina may ask for Calia's help in regards to her undead brother? his new model has white eyes, like Calia is described to have after being rezzed. maybe this new model comes into existence after a Calia intervention, and the first example of a lightforged undead? whishful thinking