The wise and wizened former leader of the Circle of Knowing, a fellowship of learned individuals hailing from the far-northern island nation of Sharlayan. In seeking to forestall the calamitous arrival of the Seventh Umbral Era, Louisoix invoked the power of the Twelve, Eorzea's pantheon of guardian deities. Alas, he disappeared amidst a blinding light following the ritual, and has not been seen or heard from since.
Well, that certainly doesn't sound very dead...
For the record, yes, I am still pretty against him making a return. End of an Era was meticulously crafted to be emotionally hard-hitting based entirely the implication that he sacrificed himself. If that was a lie, it was a cheap shot and it ruins the sentiment of the moment. Almost everything I've seen in this game says SE is better than that in FFXIV (inb4 "But, Lightning!"), so here's hoping they work around that, somehow...