I audibly screamed at this. I was absolutely shocked, this is fucking awesome.
I was suspicious at first, seeing how Atlus would NEVER announce something that wasn't announced in Japan already at a western event. Almost always, Atlus announces things at their own events. The most recent exception I can think of is announcing what came to be known as SMTV at the Nintendo Switch Conference in 2017. I thought maybe this was something about Persona Q2, but then was thinking "Why would they take time at the Game Awards for that?!"
Then I saw the envelope with the Smash symbol and lost my goddamn mind.
Thats a big reason sure. But also i feel to put Persona leapfrogging SMT is such a wrong thing to do.
As someone who much prefers SMT to Persona, and wish they did either Jack Frost or Demi-Fiend, I totally understand them doing Joker and Persona instead, and it totally makes sense. Honestly it probably makes more sense. Yes, Persona's roots are in SMT, but Persona has popularized the broader MegaTen franchise and given the popularity of Joker, it makes sense. I would bet that Joker's moveset will have more than just Arsene for Personas, and those will of course be SMT demons, which while those are in Persona games, they would also pay homage to SMT. Also I would think there might at least be a music track or two from SMT, I feel like that would be appropriate.