It looks like when Final Fantasy XVI debuts in the summer of 2023, it will arrive as a PlayStation 5 exclusive, and will remain as such for at least six months. This information comes from a marketing video from PlayStation itself, where a brief clip of the game is shown alongside the following text:
"Final Fantasy XVI anticipated Summer 2023. PS5 exclusive for six months."
<social>https://twitter.com/PlayStation/status/1589603576648798208</social>
Essentially, this seems to shut down any hope that a PC version will be on the scene any time soon, despite the fact that during the game's initial reveal, there was mention of a PC version, although that has since been brushed aside.
It does also give an idea of when the game could arrive on Xbox Series consoles, although since PlayStation and Square Enix seem to be very well connected these days, Final Fantasy XVI coming to Xbox right after the PS5 exclusivity lifts is probably rather unlikely, if it ever does debut on the platform at all - Xbox players are still waiting for Final Fantasy VII: Remake, for example.