The horsepower-race with respect to the current Nissan GT-R is ongoing and nothing will stop it, not even the limitations of the standard setup. It seems that 800bhp was not enough, 900bhp was just a small increase and that the real numbers are above a 1000bhp.
Switzer Performance Innovation is the real player in the game of achieving this magic goal. Although, it seems they have reached it. The video below shows a Nissan GT-R on a dyno. The results are a whopping 951hp on all four wheels and 804Nm of torque on all four wheels.