Honestly I'd quite like for FFXVI to be set in the universe of FFXIV, possibly before one of the earlier calamities, or on the First before it was flooded with light, or the Thirteenth before it was consumed by darkness. There's so much potential there for single-player experiences to flesh out the prior history of the universe of XIV from before XIV started, without it being confined to books.

Plus it'd be a good stepping stone to lure more people into XIV proper.