Unless it was a sequel and Morgana comes back as well?
I don't see a direct sequel happening tbh, and I also don't think a main character will be recurring within the next generation of the franchise. I'm not suuuuper knowledgeable about Persona pre-P5 though. What I
do see happening is Atlus continuing to milk the living hell out of Persona 5 for quite a few years, probably even some after P6 happens. We still see some new P4 stuff, after all.
One thing P5 does have going for it in the potential longevity department is that it seems the West was much more interested in this game than previous ones, and its growing quite a bit.
At the end of the day, we still need a few things to happen:
A) Atlus and Nintendo to agree on putting a character in Smash
B) Sakurai/Atlus/whoever would be making the final decision to find Joker to be the best fit
Feels pretty unlikely, but likely enough to give me hope. Of course I'm not keeping my hopes high at all, but I can dream. And while she was voted in, Bayonetta is proof that dreams do come true in Smash (for some people...)