In an interview with Nintendo Enthusiast, KINGDOM HEARTS series director Tetsuya Nomura confirmed that there are currently no plans to port the previous KINGDOM HEARTS games to the Nintendo Switch.
Square Enix had investigated porting existing games to the Nintendo Switch, but found that it was "technologically difficult" to accomplish. Despite the limitations, Nomura finds the console to be very "appealing" and "has always to do something on the console". Nomura has also stated that it is possible for other games he's worked on to come to the Switch, but did not specify which ones were likely.
Read Nintendo Enthusiast's feature of KINGDOM HEARTS Melody of Memory!
Thanks to forum user MATGSY for the tip!