In an interview between IGN and Kingdom Hearts Series Director Tetsuya Nomura, the topic of the Kingdom Hearts series coming to the Nintendo Switch came up.
Nomura told IGN that it "maybe possible" for Kingdom Hearts 3 to appear on Nintendo Switch, but only after the game is complete on Playstation 4 and Xbox One first:
“The Nintendo Switch is definitely a very interesting piece of hardware, but if we lightly say, ‘Oh yeah, we’ll be on the Nintendo Switch,’ I’m sure people will come back and say, ‘But what about the PS4 and Xbox One? We want them out first. Don’t focus on other platforms,’” Nomura told IGN. “So for now, we want to focus on what platforms we’ve already announced we’re going to be releasing Kingdom Hearts 3 on. And so after, perhaps, maybe we can start thinking about other possibilities.”
Nomura didn't dismiss the collection coming to Xbox One either, but isn't sure demand exists outside of the West:
“Just like with the previous answer, if we were to announce yet another non-Kingdom Hearts 3 [project]...people are going to be like, ‘Hey, what’s going on?’ So we will want to focus on releasing on the platforms that we have already announced,” he reiterated. “Do the Western audiences want Kingdom Hearts titles on the Microsoft or Xbox platforms? Japan might say ‘well, we don’t want any more on Xbox.'”