I'm pretty sure of 2 things. They will fuck up Azshara and N'Zoth like they did with Kil'Jaeden and Archimonde. And that is VERY sad.
This is because by the looks of it the game will start with horde alliance conflict and then turn into soemthing more "sinister" with Azshara, wich is confirmed we will face. This means we will have another expansion where a HUGE lore figure pops out from nowhere with no real story being told, and then just die like a clown.
Given how things shaped up in Legion i'm pretty sure they will do the same error again.
If you want to give me Azshara, You palce that fking Naga on the box art and you say "this expansion is about Azshara motherfuckerssss!" and then the expansion goes around that with a rich story. That is what they should do, not this bs where you start with a war, just for things to turn in a compeltly different way to fight azshara (together i guess....) i hate this kind of stuff.
They did it ever sicne Cataclysm as well. No clear villains, just go on with whatever they throw at you with no clue what you're really fighting. Some may like it, but i HATE it. I don't think this approach has given us much positives to be honest. I'm still absolutely pissed on how they dispatched Kil'Jaeden in such a ridicolous way. We are talking of a guy who IS the LORE of this damn game alone, and the best they could do is relegate him to a mid expansion raid, where he pop ups from NOWEHRE, with no story told whatsoever. Jus put him there and go die. Kil'Jaeden SHOULD have been the ONLY choice for the final boss of Legion. Yes Argus makes sense given how they went with the story, but he is a nobody compared to Kil'Jaeden, and has the charisma of a dishwasher machine.
Overall, this is all to say that i really wish they would jsut go a step back, and focus more on the imporant vaillanous figures in wow lore (wich are quickly running out btw, at least the most notorious ones), and they would stop with this "you will fight something somwhere at some point" just to see important characters die as quicklly as they came.
Of course, i could be wrong (i really hope!) and BfA (wich overall i'm hyped about) will treat Azshara and company like the big badass baddy that she is.