I don't know it's been posted before but (UNCONFIRMED, of course), the new Expansion could be named Forspoken. Does seem to follow the naming trend of one cognate word titles. However, I'm drawing a blank as to what it could mean outside of a grander Hydaelin/Zodiac connection, the climax to the Hydaelin/Zodiark plot we've been expecting.
Personally, I'd welcome Old Sharlayan for its aesthetics and themes; Garlemald seems the obvious place for now, but the Empire was "obvious" for 5.0 before FanFest and 4.5 swept the rug and brought us to the First.