Just a quick thought:
We often see things in X.3 that seem to foreshadow mechanics and stuff in the following expansion eg like the the Netherlight Crucible being sort of similar to Azerite armour.
Anyway the Horrific Visions show a alternative version of a location, namely Stormwind and Orgrimmar, but under the control of Nzoth. Since most signs point to a death expasion being next I was thinking we might see a similar idea used for the Shadowlands. Rather then enter Nzoth vision of Stormwind we enter the Shadowlands version of an area. This could be used as a new island like system in 9.0.
It's a thought.