I just hope they continue to clear up known foes for the near future before writing deeply into an void lord expansion off-planet.
Azshara's Naga Army never been truly dealt with, Vash'jir was only an outpost at best, due to the Rift connection to Abyssal Maw/water elemental plane.
As is the uncertainty of some Old Gods. Only Y'shaarj seems truly dead in canon, altho there's a whisper from the priest artifact.
Xal'atath whispers:
It is ironic that the weakest of us may be the ultimate victor. C'Thun, Yogg-Saron, Y'Shaarj, and... well. Only one would remain to consume the world, that was always meant to be.
C'thun been fairly unknown, previously known as dead, then we got a comic that transformed Cho'gall to his spiked eye-body form.
And now we got a "stab" wound in silthus with energy seeping out neaby Ahn'qiraj.
N'zoth seems certainly the most powerful remaining named force on the planet. Speculation exist the Kraken like Ozumat are actually his minions/similarities.
N'zoth also often mentioned as the one beneath the waves, we get some tentacle corruption in places like Vasj'ir and BlackFathom deeps, especially BFD tentacles look a lot like Kraken/Ozumat-style.
Not to be confused with the "whale" like kraken.
We deal with kraken eggs in Broken shore, briefly, Khadgar mentions they gotta be dealt with. I assume he means before they mature/grow powerful. As they can take down ships.
I wouldn't be surprised if we get an island expansion, to see a lot more Squid/Krakens.