How would they do that? PJSK is a touch-based game, how do you port that to consoles?
In technical terms, is called "touch-button mapping": basically, the dev team can assign some touch operations to specific buttons of the gamepad/keyboard, even the mouse.
Also, both Android and Apple iOS games already have native support for buttons mapping (since you can play many games on smartphone and tablet with an external gamepad, like the Dualshock4 of PS4), and the help of Atlus would be great for converting to PC/console gameplay all those parts that need more work.
Atlus in fact is responsible for SEGA for all the ports of console games to PC (think of Persona series, but they also helped with Project Diva and Yakuza series). It is common for japanese mobile games to have some complete offline version on PC/console after some years.
I would say, 80% of Project Sekai is already perfect for a 1:1 port to PC/console. If they wanted, it could be ready in a matter of 6 months. It is more like when the upper management will decide that it's time to release a complete version of the game. But again, there are many examples of mobile-only games that were successfully released later on console/PC.

It was, 2 years ago if I remember well, there was an official livestream where they talked a possible PC version of Project Sekai, and they said "it wasn't planned for now, but will keep listening to fans requests".