The fact that you keep having to go "b-but there's the Lifelands and Pantheon of Life?" two things
that aren't the Emerald Dream, should be a red flag for you indicating just how done the concept is. Because the reality is that you understand that the Dream is already dealt with so much that even
you envision an "EmEralD dReAm" expansion as not being the Emerald Dream, but instead some other completely different, yet to exist place with completely different, yet to be defined powers and a completely different, currently non-existent threat that all have absolutely nothing to do with the Emerald Dream, beyond both being associated with "Life".
The fact that a theoretical "Lifelands" might exist doesn't change that the Emerald Dream has been dealt with, and in all likelihood, if such an expansion were to come out, the Emerald Dream's only role (if it had any at all, which is doubtful) would be as some sort of entryway or hub into the actual realm of Life. Like Icecrown in Shadowlands, the Maelstrom in Cataclysm, or Dalaran in Legion.