It looks like Persona 6 will release across multiple platforms at once.
In Sega Sammy's quarterly earnings Q&A with investors (as reported by Persona Central), the company's president Haruki Atami teased plans for the next main Persona game, specifically regarding achievable sales targets for the next main game in the series.
"We believe that it would be possible for a major Persona title, such as a numbered release, to sell 5 million copies in its first year by releasing it on multiple platforms and simultaneously worldwide from day one," the Sega Sammy representative director said.
That question specifically came from an angle about a Persona game one day selling five million copies in a single year. No Persona game has ever achieved this, and Atami clearly believes that it can only be achieved by a main Persona game debuting across multiple platforms at once.
So if Sega wants Persona 6 to sell as well as possible in its first year (which it obviously does), it's going to need to release it on multiple platforms at the same time. This looks to be the direction for Persona 6 when it eventually launches, going by Atami's comments.
This would've been unthinkable for Persona games in past years, but it's now become the new standard for developer Atlus. Persona 5 Royal is now on PlayStation, Xbox, PC, and Nintendo systems, while spin-off Persona 5 Tactica will launch across all platforms simultaneously tomorrow on November 17.
Even next year in 2024, Persona 3 Reload will launch across all the same systems at once on February 2. Atlus and Sega have new attitudes for the Persona series thanks to its overseas popularity, and Persona 6 will feel the results of that.
Persona 6 could be themed around the color green, whenever it eventually launches.