It looks like we were wrong. The PS3 exclusive, which we thought would not be revealed at Ubisoft's press day in Paris today, appears to be the first person shooter, Haze, according to our reporter on the ground.
Whether it can replicate the success on the PS3 that Gears of War had on the Xbox 360 only time will tell. As we speak, the press haven't been able to go hands on with the game as yet, and have only been shown an old trailer.
The official Haze website appears to confirm that Ubisoft's first person shooter is indeed exclusive to PS3.
We have a few details on Haze: here. Screenshots and further details should surface later today.