This is the first expansion they are holding out on info cause of the QQ.
They remove terrible ideas and forums go bat shit crazy about removal of content, so no wonder now we dont know anything apart from a few things.
It was also obvious from the video when they showed the Sea Priest Kul tiras dude that they are some sort of N'zoth/Naga minions involved.
We also knew from Legion Aszuna quests, and the Eye of Azshara that its incoming, not sure why people are surprised.
Now the question is, if we are gonna have Dual Tier 1 Raids like Nighthold/EN or she is gonna be full T2 like ToS.