Those of you hoping to get some version of older Kingdom Hearts on the Nintendo Switch are gonna be mighty disappointed. Ever since Kingdom Hearts III was revealed, fans of the Switch have been wondering if Square Enix would get around to releasing everything from the first two games (as big and non-sensical as that collection would be) onto Nintendo's current console. Not only did KH3 skip the console altogether, but no word ever came out about trying to do anything with Nintendo until the new Kingdom Hearts: Melody Of Memory game was announced on a Nintendo Direct. Once that happened, yet again, fans got hopeful that the two could do business to bring the series to the Switch. Unfortunately, that's not going to be happening at all.
In an interview with Nintendo Enthusiast, they did an interview through a translator with director Tetsuya Nomura, who basically confirmed the news. But it wasn't for lack of wanting to do it or any kind of exclusivity, it has more to do with the tech.
Through a translator, Tetsuya Nomura confirmed there are currently no specific plans for more Kingdom Hearts games on Switch. Square Enix did consider ports of existing games for Switch in the past but found that it was technologically difficult. However, Nomura added that he believes Nintendo Switch is a very appealing piece of hardware and he had always wanted to do something on this console. Additionally, while he cannot speak for games at Square Enix that he isn't associated with, Nomura did express that it is possible another game of his could come to Switch.
So maybe, somewhere down the road, if they're in the mood, there might be a chance of getting a new KH title to work on the Switch. But as far as porting any of the old ones, you can let that dream go.