Port is such a bad descriptor. I believe 90% of the people who believe the game will be a """port""" mean "updated version" instead. A half-step between 4 and something totally new. Port carries the connotation that it's the same thing, maybe with a few new bells and whistles, on another system.
But imagine 4 and this game were on the same system. Use the Capcom fighting-game model as a very loose rubric of iterative releases. I believe people are suggesting something in the vein of 4 being the vanilla version whereas Switch will be something roughly akin to upgrades of games which extensively build on their own framework as they overhaul and refine, but ultimately retain the blueprint of the original creation. Even should they not brand it as such.
It's not really a port, it's just not really an entirely new title either. I don't think there are any perfect 1:1 examples of what is being theorized, which is why it's difficult to explain or envision the genesis, and partially why people reduce the term, to everyone's detriment, to "port".