I think we see both scenarios in this expansion, just like we see Broken Isles + Argus in Legion. "Oceans" more Old Gods oriented and Northrend to lead us from Old Gods to Void themes.
All the datamined files lead us there: Azshara, N'zoth... Jaina but we don't have yet all the information to link the dots...
Sylvanas, the Aspects, Chromie scenario, Odyn and the Titans keepers of Ulduar, Old gods and Ethereum are all things related to Northrend...
Sylvana's plot lead us in Northrend for "life/death theme": that means Shadowland + Odyn but this involve even Bolvar. Also, Sylvana's echos was linked to Alexstrasza in the "End of Time" dungeon (just like Tyrande was to Ysera and Jain with Blue dragonshrine). There is even a link between Dragons and the "undead". Infact, the not-living created by Galakrond was the first form of undead threat that Azeroth has faced and now, thanks to Xal'atath whispers, we know Galakrond was corrupted by Old Gods.
Also, in Legion we discover that the Ethereums got access to the Nexus where they try to became a Void army using the surge needles to bore into the Twisting Nether and call up void energies. Azuregos now is into the Nexus to protect it but, we dont know why Azuregos was there and if he could be corrupted.
So, in Cordarra, there are all the tools for drag void energy from Twisting Nether to Azeroth.
There are materials for more than one expansion, but we was think the same about Emerald Nightmare/Legion and Argus.. and we got all of that in just expansion.