It was just part of their fiscal announcement:
Currently Remedy is developing a sequel to one of the most popular games in the world in cooperation with the Korean publisher Smilegate, whose long-time success CrossFire gathers 650 million registered users and over one billion dollar yearly revenues.
Remedy is also working on a game project codenamed P7. The company’s strategy is to release the game on a wider range of platforms, which is why Remedy is developing its Northlight technology also for PlayStation 4 consoles.
The former was known, they're doing the single player for it.
They's a tiny chance it's something related to Alan Wake 2 which they said they were going to look at again after finishing Quantum Break. But that's the only thing they've ever named.
Thread title is funny since they were never "multiplat" as both the Max Payne games were ported to the consoles by Rockstar.