Culture doesn't just vanish because you emigrate/immigrate. Nomadic warrior peoples are not going to suddenly stop roaming or fighting territorial disputes just because they've been displaced. Assimilation is not instant, it takes years if not decades (I should know, my entire family immigrated to the U.S. back in the 70s and we're still VERY cultural w/ regards to our ethnic background).
It's like adding two tomcats who are new to each other to a household that already has two pugs for dogs. Staking out and fighting over and establishing territory is still going to happen... and the dogs rarely even care. (I've done this). I see Xaela in the same vein. Eorzea is just more territory over which to feud ("We earned the trust of the Gridanians, Johnston, YOU cant live here" "Well, Avery, Thanalan sucks, so we're moving in!")
It's like adding two tomcats who are new to each other to a household that already has two pugs for dogs. Staking out and fighting over and establishing territory is still going to happen... and the dogs rarely even care. (I've done this). I see Xaela in the same vein. Eorzea is just more territory over which to feud ("We earned the trust of the Gridanians, Johnston, YOU cant live here" "Well, Avery, Thanalan sucks, so we're moving in!")