The work they'd need to do for a Switch version is largely the same sort of changes they'd make for a mobile version.
When you consider that, it suddenly doesn't sound as unlikely.
FFVIIR and its sequels are going to be a huge part of SE's business this decade. It's crucially important that they have a large addressable market for FFVIIR-2.
I used to be of this mindset, but I'm not anymore. You can see tons of PS4 games like Monster Hunter World Iceborne and Resident Evil 2 Remake running on a GPD Win 2, which is overall probably weaker than a Switch and these games have no real optimization specific to that hardware.
MH World Iceborne even runs at a very decent 30+ fps.
Here's Resident Evil 3 Remake, which is probably a better looking game than FFVII Remake
Again this is really no hardware optimization. I think all these games can in fact run on a Switch. Is the undocked version going to win a medal for sexiest looking version? Of course not. But with a bit of optimization at 540p undocked I think they can get a 30 fps version.
It's a question moreso of are the sales of a 1+ year late port worth it ... maybe. FFVII is a flagship brand for Square-Enix, the same way things like Witcher 3 are for other companies there may be a desire to get a version for Switch to tap into an extra market, probably Japan in specific you're looking at 500k+ sales there alone.
They were willing to put in the time for DQXI ... FFVII Remake I think would likely outsell that fairly easily, probably similar sales in Japan + higher sales in Europe and North America.