Hmm... seems a bit premature or speculative.
The angle of ultimate betrayal is something that had been promised before, so this is backtracking/retreading in order to make that up to us. So that would be a good feature to finally come through on.
While a third faction seems like it would make sense from a plausibility standpoint, and business, generally speaking it sounds a little like it's putting the cart before the horse. Possibly disinfo if not made up. Presuming it's true, I can see another HK droid in the fray. I can see chaotic neutral/fringe characters.
All in all, I hear Emperor Vitiate made a comeback in shadow of Revan (Don't spoil it for me with details) which wasn't entirely unforeseen, so as it stands this is probably filling in the blanks for the time being. Possibly building up to the next expansion or whenever the Emperor returns for his big rematch. As it was in the Revan novel, Vitiate's own empire was at odds with him back then, 300 years prior. Considering what he did initially over a millennium ago I would not put it past him to turn on his own people again while harboring a loyal but naive following... again...
Now just to get confirmation that the force essence was in fact Kreia, and that Arren Kae and herself are one and the same.
We'll murder them all, amid laughter and merriment...except for the few we take home to experiment!
"I cant see S***! --YOU GO TO HELL!" --Tourettes guy