Not a chance!

I don't see it happening.

It is very likely we will see either XVI or direct sequals to XV. 

The gen will last at least another 2 or 3 years. By then the FFXV team has to put out another game. Theres also the possibility they have another team that has been working on it since the agni philosophy thing. I strongly believe that will be the next FF. Would be wasteful not to use that material.

More likely we see FF15-2. They spent a lot of money on that engine and world, I'm sure they're going to use it as much as they can before scrapping it and moving on to 16.

Not something I'd be against, though. I think all the ingredients of FF15 were right, just directed and combined a little haphazardly, and they could still do great things with those characters and that setting.

Maybe but it depends on how much they're prioritising FFVIIR. I'm more interested in whether they ever do a turn based active time battle system again. Don't get me wrong I enjoy real time action battles but it would be good to play a FF with a more traditional battle system. They could really put detail into the magics and summons and make the physical attacks look awesome.

I don't see how you can acknowledge the issues with FF7R and KH3 now, and not think those will be issues with FF16. Not a chance in hell those games have been anounced ages ago and don't seem close to being done, but a game that probably won't get announced until next year at the absolute earliest, being worked on by the same people who just finished the baggage-ridden FFXV, will be released this generation.

Hiroyuki Ito directing FF16 would make me super happy. He's been with Final Fantasy since the beginning, directed my favourite entry (FF9), and isn't afraid to take risks while still maintaining an old-school feel.

My guess is we'll see FF16 as a cross-gen title around late 2019/early 2020. I can't see them wanting to wait until the next generation is fully established, and i expect they'd prefer to take further advantage of the tech in FF15 before they start from scratch again. The current version of FF15 appears to have taken around 4~ years to make, so with a now experienced team and pre-existing technology, having FF16 done in 3~ is doable. TW3 was finished in 3.5 years, SE just need to ensure the team stays focused :p

For reference, they managed to finish FF13-2 in 1.5 years, down from the original's 5.5 years. While it was also a smaller game, it's not 3+ times smaller.

i think they will release it between generation... 

Very unlikely, in my opinion

Only way I can see it happening is if they've working on it for a while as of now, even if it just were pre-production stuff, having a clear mind about what stuff is actually going into the game will make it easier for the dev team to finish the game before 2020. May end up as the PS4's swansong if it gets lucky.