The truth is we don't know her fate.
She may be dead. She may be alive. She may be Scourge or Forsaken. She may be with the EBon Blade of a free agent somewhere.
We just don't know.
The novel Arthas hints she is dead...but without a body - heck, even with a body since we have Resurrection available - that's far from a definitive answer.
My own thoughts are:
a: that Calia is too interesting a story for Blizzard to just ignore her.
b: that Calia as Forsaken adds nothing to the game. Since you can't change the character of the Undead, all she'd be would be Sylvanas. But the Forsaken don't really we her anything, never mind their allegiance.
c: that Blizzard will get the biggest bang in bringing her back if they bring her back alive, and for the Alliance. Maybe not rabidly anti-undead...but still pro-Alliance. Both sides get a workout then. Make her neutral and she just ends up on the sidelines. Make her Forsaken and she is just going to be Sylvanas. Make her Alliance and she can act as means to get the Alliance and Forsaken stories moving.
However...if she is alive, she is running out of places to hide. Short of finding her marooned or imprisoned somewhere, finding her stranded in Kul Tiras is going to be the last way to really bring her into play. Blizzard does seem to want to do something with her though, so I don't think we'll find her dead.
Could she come back as a villain? It seems doubtful...but not impossible. Thing is, the Scourge are on the run, the Forsaken "aren't" villains and the Crusade are decimated...so as a Villain, she'd likely be fairly weak unless she's acting the patsy for someone else.
Unless they are Lordaeranian refugees. Also...lets not forget a good many people from Stormwind grew up in Lordaeron and can very easily see it as home.
Who was able to do what he did because the Orcs did nothing to stop them. Nor does the rogue Forsaken excuse the little fact that everything in Undercity was ordered by Sylvanas, carried out with her permission and involvement and took place over several years while being part of the Horde.And he continues to rant about orcs later too, despite this whole incident being because of rogue Forsaken who sided with the Legion
And is it ranting? Or trash talk designed to inspire his men and make Thrall and his Orcs angry? He was a gladiator you know.
The other aim was to kill PutressNot to mention he went there with the sole intention of capturing UC for the Alliance even after learning that Thrall was going in to punish those responsible.
EJL