But then comes the thing that we gotta remember: Japan. The Switch has outsold the PS4 in lifetime sales over there, and most devs and primary traction are now starting to shift over from the PS4 to the Switch. Not 100%, but it's happening. The most recent news of God Eater 3 coming to Switch would be a testament to that.
So I'd be honestly shocked more than anything if they're just going to have all the Persona 5-related projects just be PS4 only, when they'll be completely neglecting a huge opportunity to make some insane bank releasing something on the Switch, just basing off of marketing to the Japanese alone. Japan loves Persona 5, they love the Switch, it'd make perfect sense.
And to be fair, if Nintendo's choosing all the fighters for Ultimate's DLC and out of ALL the characters they choose, Joker from Persona 5 is one of them? While that would be striking the iron hot, I don't think it's because "hey, he's cool".