I'm just curious as to why I haven't heard rumblings of that. The series has been on Nintendo systems before, with a PS3-PS4 version of the collections meaning they could easily run on the Switch. 

3 is a trickier thing, but I have a argument to such questions as 'can it run'. 

...Is it like Persona mainline games where there is probably a exclusivity contract? Or is it....something else? 

...Or will I just see Sora in Deep Jungle in HD in the Jan/Fed 2020 direct.

Both are long overdue. Hopefully SE gets some sense knocked into them.

A switch port for Kingdom Hearts collection could come maybe after the xbox version, but as for Kingdom Hearts 3 some information has been given in the past saying that square enix is interested in the idea but an ex gameinformer employee said that he got reports it wasn't working out getting the game running on switch, but square enix got Dragon Quest 11 working on switch which also runs on unreal engine, even though they had a good number of issues getting it onto switch but that was because it was an older version of unreal that switch couldn't support if i remember correctly. So anything is possible but i just don't know when, plus they might want to focus first on a possible PC port first if anything.

https://comicbook.com/gaming/2019/02/17/kingdom-hearts-3-nintendo-switch-release/

I would assume KH Collection would come to Switch at some point considering SE announced they were coming to Xbox. Same for KH3 maybe.

Also, wondering if we will ever see these games on PC.

Never played any of that that I recall. I typically avoid sequels unless I play the first games. So I'd prefer the collection over 3 to see what all the hype is about.

You're saying witcher 3 isn't a good argument? What would you consider a good one? The switch's specs were all the argument needed but we also got ports like these that prove it anyway. Of course it didn't take a lot of money, it's a port. Even if it was obviously more expensive than regular ports, that's still a small fraction of developing the whole game and that goes for any intensive ps4 game getting a switch port. If SE gets some sense, we'll see KH 3 running on the switch in 720p and same framerate as the other versions (with downgraded graphics).

Dragon Quest XI S is 900p/30fps on base PS4. And the Switch version is not to far from there. Sure, Kingdom Hearts III has better graphics in general... But Dragon Quest has far bigger maps. I think they can pull of a 720p/540p alla The Witcher 3 with ease... maybe even better.

As for 1.5 and 2.5 HD Remix... The only reason I can think of it not being on the Switch yet... is the file size. I think the game sits at 50 GB con PS4... even with compression, I don't see it going under 25-30. They are gonna need a 32 GB card... and I guess SE doesn't want to pay for it.

If it is more demanding or not requires a whole other analysis to know but that isn't relevant. It would translate into lower res and downgraded graphics to the switch and it obviously doesn't take a lot of time/money/effort compared to other ports.

Wow, didn't know those Kingdom Hearts games were so big.  File size is actually the much bigger limitation.  People make a big deal out of the processor and RAM, but that can be worked around, especially with a game with cartoony graphics like KH3.  But studios don't want to pay for an expensive cart. 

If file size is the limiting factor here, then we may get some KH ports near the end of the Switch's life when the price of carts has gone down.  KH games have been on Nintendo handhelds before, so there is some precedent.