unfortunately, chances that ultima and dalmasca will be involved are close to 0, because:-
1-side content
2-everything related to ivalice was 100% scrapped

this is definitely the biggest clue to why people believe that the game's team skipped a planned garlemald expansion, it seems bozja was supposed to be continued in the following expansion, but they just closed what happened to the 4th leigon in the codex shortly after they released the final part of bozja
these are 2 very strong reasons why we can't expect ANY high seraph involvment, beside, look at how they speed-ran old lore in endwalker like path of the twelve, they just want to close these and build new lore and new stuff, they even recently published a lore\story builder job listing for XIV
the twleve questline was a big chance for the deities to talk about older eras and calamities and reveal more lore, but it is what it is i guess