Today, Cygames announced a fighting game based on the popular mobile RPG Granblue Fantasy, called Granblue Fantasy Versus. This game is developed by Arc System Works, and it will be released in Japan in 2019.
While this wouldn't imply anything about the Persona series on its own, what is remarkable is a supposed leak from the Japanese text board 5channel (formerly 2channel). On December 10, 2018 in a Super Smash Bros. Ultimate discussion, an anonymous user posted the following:
Joker
The stage is Mementos
Jack Frost appears on screen with a skill
Marketing of P5R (complete version) and P5U (fighting game)
P5R is 2019
P5U is delayed because Arc is busy with the development of a Granblue fighting game
This information is certainly not conclusive, however it was a post made five days before today's announcement of a Granblue Fantasy fighting game. There had been no rumors of this beforehand.
More at https://personacentral.com/rumor-pe...plete-edition-2019-super-smash-ultimate-leak/, including the details of the supposed second Smash DLC (Dragon Quest character).
Worth noting that Vergeben talked for a long time about a Square Enix rep for Smash coming.