No, no, no, no time travel plz.

It'd be AWESOME as a raid (savage or alliance), but not as an expansion. WoW got me traumatized with that.

It'll take a long while before we go to Garlemald, I suppose. And I don't see us going there to conquer it, maybe there'll be a truce at some point? But not on 5.0, maybe 6 or 7.0
Meracydia and Thavnair would be my best bet for 5.0. And there's also the New World to consider.