When I first started playing in classic wow there was so much we could see coming in the future, the Lich king obviously, Illidan was still out there somewhere, Deathwing was missing as well I believe, the legion was obviously a threat that would need to be defeated one day as we eveanutlly would get to meet the titans as we came to argus and defeat them. Oh and the Emerald Nightmare was obviously going to get a raid evenutally as well, also lots of people have being expecting a Kul'tiras and Zandalar Expansion for a long time.
So my point is there was a time when it was nearly obvious what expansions would come, it wasn't obvious when but that they would come at some point there were plenty of themes in the game that had being started but not explored to their potentinal, the breadcrumbs had being left around but these days I struggle to think what will come next we've killed so many legendery figures and ended so many storylines from the early days that took so long to end.
My only ideas are literally another Void Lord Expansion to follow the bread crumbs this expansion will leave with old gods influencing the War. MAYBE a bolvar the lich king expansion, so two POSSIBLE ideas. In classic wow there were so many obvious things to follow but now? so much lore has being used up. Any ideas folks!
TLDR: It feels like wow is running out of the plotlines that classic launched with, Void lords and Bolvar the lich king are the only two hypothetical threats I can think of when classic had lots of hypothetical threats left understandably.
UPDATE: Obviously they can come up with new storylines! I never said wow was dying or any shit like that! I am just saying they will be less predictable now! That's it, that's all! Most had roots in warcraft 3 and classic wow and that is looking less possible now, so we'll get more unpredictable expansions and possibly utterly new storylines never seen before in any shape or form and I wonder what!