There is NO definite evidence of a 550 hp version, none at all. Anything you have heard in regards to that, is purely speculation.
(Unless I missed something, guys?). The Top of the Top may be seated at 460 hp most (at least in my book). The only reasoning that I have, is that the LS7 is dying, and it's replacement is the LS9, (or blown LS3). Which is equally expensive; what with the forged crank, and strenghtened parts. And at prices like that, the LS9 slowly drifts out of Camaro territory.
I'm not ruling out a 500+ hp Camaro, at all. But the evidence points against it as a mainstream Camaro. But if a 500 hp version does come out (which I think it will), it'll probably be a limited-numbers, high-priced, "Shelby GT500 equivalant" Car.
Sorry if I just made you cry...