Guerrilla Games, developer of PlayStation 4 launch title Killzone: Shadow Fall, has been working on another currently-unannounced IP for two-and-a-half years already. Of course, when you have a studio with around 200 employees you can do that kind of thing.
In a video designed to introduce the team behind Killzone: Shadow Fall to Japanese gamers, executive producer Angie Smets mentions the new game, presumably coming to PS4 as well.
"We are working on a new IP. We started on that already two-and-a-half years ago," Smets said. "Unfortunately, we cannot share details of the new IP, so you'll have to be a bit more patient until then."
You can find the exact quote in the clip below (at the 2:20 mark).
It's not uncommon for Sony-owned studios to work on two projects at once. Naughty Dog, developers of Uncharted and The Last of Us, is another studio that works on two projects at once. In fact, with one side of the studio working on a new Uncharted for PS4 and the team that worked on The Last of Us just about wrapped up, Naughty Dog is beginning to look at new projects to tackle. There's demand for a sequel to The Last of Us, but Naughty Dog remains split 50/50 on the idea. Some are even hoping for The Last of Us on PS4, but, again, Naughty Dog remains tight-lipped on the possibility.