I thought this “Sylvanas becomes the new Arbiter” might happen long before the 4chan “leak” (in case anyone asks, no, I’m not - and have never been - a 4chan member).
I even did a thread about it; Sylvanas will become the new Arbiter
While I think that’s the stupidest thing Blizzard could possibly do with Sylvanas, I think that’s what’s going to happen and the original intended direction for her story, as much as I would like to be wrong about this.