From what has been spoken and shown in the 5.4 trailer...
Looks like Garlemald, Sharlayan, and even Meracydia are up in the air here and possibly none will be the location. Large amounts of Garlemald are reduced to rubble apparently, and we're starting to see towers and whatnot appear in Nym, what looks like a tempered soldier in Ala Mhigo, and several other things. I don't think we're going to Garlemald, I think whatever is about to happen is going to attack us straight in Eorzea.