FF7 Remake Director says the trilogy is "not the end" of FF support on the platform:

"This is certainly not the end, not just with the Final Fantasy 7 series, but we want to continue to have the Final Fantasy franchise be loved by players around the world. And this is something we’ll continue to strive to support.”

https://www.gonintendo.com/contents/53229-final-fantasy-vii-remake-director-says-this-is-not-the-end-of-series-support-for

Hopefully SE will learn a thing or two from Capcom who has been really successful with their multiplatform releases. Yes, MHW has its issues, but their games are selling really really well.

Easy Allies have posted an interview with series director Hamaguchi which has some interesting insights:

“Right now the team is currently working on porting Final Fantasy VII Rebirth to Switch 2. At the same time we’re working on developing the third game. As for the third installment we do have designated teams working on each platform so our multiplatform approach won’t impact development. Development of Rebirth for Switch 2 and the third instalment are going very smoothly.”

"As for the Xbox version, like many other publishers, we did see some issues with the lack of memory [on the Series S] platform compared to the other platforms. As for the Switch 2 version, we actually have the main dev team working really hard on it, I think as a result, we are really confident in the end product."

I know Switch 2 is inferior to even Series S in most ways, but I think FF16 could get a Switch 2 port. I know the game fell below expectations for sales, but I think it could sell better on Switch 2 than Xbox which they already ported it to. 

FF17 might be day and date on consoles and PC. But if it's a PS6 game with no PS5 version, they would really have their work cut out for them to port it to Switch 2. Unless new numbered FF games go on a very long hiatus, I don't think Switch 3 or whatever will be out by time FF17 launches. 

Yeah I do expect we will see FF16 ported to Switch 2 eventually, though Square have said they are prioritizing FF7 Remake/Rebirth first. It would need a lot of work though as it wasn't a particularly well optimized game on PS5/Xbox. But yeah, I agree it'd sell better on Switch 2 than the Series.

The way things are going, almost zero chance FF7 Part 3 won't have a PS5 version. I expect there will be hardly any PS6 games that aren't crossgen until like the 2030s.

Switch 2s are going to explode trying to run Part III.

Part III probably won't be much more advanced than Rebirth, as its targeting Switch 2 and Series S from relatively early in development, and high end graphics are getting more and more expensive.

This all depends on whether they move to UE5 and use its features of not. Baring in mind Part 3 would of started development about 14months before S2 came out. I suspect they won't use nanite, if they do that may be a problem for S2.  If they do use lumen, I believe it will be optional. 

The decision to bring the whole trilogy to Switch 2 was probably made internally some time ago, possibly before Part 3's technical makeup was set in stone.

UE5 is currently in pretty rough shape on Switch 2 (and on consoles in general to be frank) but if they do use it, then hopefully by 2028 or whenever it rolls out, the engine will have been reworked to work a lot better on Nintendo's system, as happened with UE4 on Switch 1 over the years.

This. If Part 3 takes long enough, it will be day and date cross-gen. Otherwise, it will be a PS5 title that will within months to probably a year and a half get a PS6 version. 

I'm thinking September 2027-June 2028 for Part 3. Square Enix is hoping and planning it will be the same release gap between Remake and Rebirth if not a narrower gap. 

Almost zero chance Part 3 launches on Xbox at the same time as PS5. I don't even think it will be day and date PC. I think it will be the last FF game that will be a timed PlayStation exclusive.