Hrm, well, there's a few ways Fio could go. With his current path, it's highly unlikely he'll live to see old age. Honestly, I see him either dying while holding the line against, uh, you people. *Waggles fingers.* Be it Garlemald comes under siege, or Fio is trying to stop the Eorzeans from razing liberating Ala Mhigo. He squares off against familiar faces, maybe takes a few out, and eventually bites the dust after having faced overwhelming odds. Or triggers a massive ceruleum detonation with the last vestiges of his strength. Because the Empire runs on ceruleum. Or he could get knifed in the back. Or hung for being a traitor to Eorzea and her city states.
I'm better than you.