FFXVI and XIV connection theory

[Enkidoh]

Exactly, also the development team outright stated in a Letter From the Producer Live a few years ago that all FF worlds are basically seperate dimensions/universes, they're not other Shards to Hydaelyn or on other planets in the same universe - names of places from other FF games that appear in FFXIV are just references to those other games with little to no direct story connection to them (they're just fanservice, nothing more):

1:57:29
Q: A lot of names from Ivalice have been mentioned such as Dalmasca, Belias, and Zodiak. Is there some kind of connection between Hydaelyn and Ivalice?
A: Maehiro: To be absolutely clear, there is no direct connection between FFXIV’s Hydaelyn and FFXII’s Ivalice or even FFXI’s Vana’diel. They are not the same world in different dimensions or time—they are their own separate worlds. However, there are certain connections to people or objects that appear in these other worlds that figure into the story of FFXIV as it has been conceived and is being told.

Yoshida: We’ll be revealing more as we move forward.

Note that was many years before they added the Return to Ivalice raid however, but the idea is still current - each FF world takes places in it's own seperate universe (despite some hinting at connections between some games - the infamous tongue-in-cheek FFVII-FFX link being one), and that will be the same with FFXVI.

As Cleretic stated, the Dissidia games already stated that every FF game is it's own independent universe loosely connected by the Dimensional Rift, but, to confuse matters, this is a seperate Dimensional Rift to FFXIV's one, so... the distinction needs to be stated (and to confuse matters even more, the other name for the FF-reoccurring Dimensional Rift is... the Void) as they're seperate things with the same name.