It's not going to be Garlemald. The empire is done already. Fractured into too many sub-factions, to pose any sort of major threat anymore.

5.4 MSQ being in Ishgard and mentioning Matoya for the dungeon, just leads us to Sharlayan. The fact that the twins dad was name checked recently and he has a character model adds weight to this. He will be a main character. If we are concluding the Hydaelyn/Zodiark arc in 6.0, Sharlayan seems the sensible place to go. A split between Sharlayan and the New World would not surprise me. There's some Garleans over there Zenos can throw at us, Alphinaud can beceom a Blue Mage, we can have a Mamool-Ja primal etc..