Others have remarked upon this before, but we walked past/through who knows how many subjugated nations on the way to Garlemald in Endwalker, none of whom were consulted (that we know of, this could be revealed to have happened offscreen later) when the Grand Company of Eorzea elected to give Garlemald an olive branch. I'd imagine that the 5th and 8th are holding territories north of Corvos and Werlyt but south of Garlemald, which could provide enough lingering tension to build a story thread off of. While at least one of these territories (Landis) is at least nominally pro-Empire by all indications, and places like Nhalmasque further north have had multiple generations of Garlean rule, I can't imagine everybody's happy about the resolution of this war going over their heads and/or still being held by Imperial legions.

Quote Originally Posted by EdwinLi View Post
At this point, I still believe they are probably saving the fate of the 10th legion for a Final Fantasy 12 theme expansion. They been building up something with it in the past expansions and I doubt they plan to just leave it as it is the last time we saw them.
While I see what you're getting at, I'd also contend that an FFXII-style story is very well-tread ground in FFXIV; A Realm Reborn and Stormblood both share a lot of DNA with 12, as well as Bozja in side content. I could see them potentially continuing the Return to Ivalice/Save the Queen thread in side content (it will be a hell of a lot of unlocks later by then), but I don't know how keen the devs are to go back to that well so soon, particularly given that part of the reason Endwalker came right after Shadowbringers was a fear that players would get fatigued of the extended war-with-Garlemald arc.