As a Hellsguard player, I admit the desire to get a dungeon at least in volcanic mountains to the northwest of Garlemald so I get a glimpse of the purported homeland. Also it'd be a way to redo and improve the environmental aesthetics of Pyros.
South Seas Islands is one of those locales I believe with 100% certainty we will physically go to, for a dungeon or sidequest mini-zone like Werlyt instead of a full map now that we have Island Sanctuary. For the Japanese love of Hawaii if nothing else.
Golmore and Fanow is something I go back and forth on solely because of the M Tribe in the Fringes repeating the same idea of Suncat village that the U village in Thanalan had. Unlike Fanow, this hypothetical Golmore would have different tree models and could include a Male NPC or two to distinguish itself.
I still think if they do a Southern Ilsabard/Othard expansion, Ivalice Raid will be mandatory or tweaked, or else major plot points and even zones will have the same vibe as "playing HW before you do the DRG quests". Landis and what its situation is too dependent on the completion status of Bozja, content that will never be mandatory MSQ.
Realistically I think Southern Ilsabard gets tacked onto a Meracydia expansion. My fear is a Doma/Ala Mhigo split of Meracydia and New World (or worse, Meracydia as one zone and all three shoved into one expac. But as the plan is to reach 10.0, I'm telling myself not to fear that.)