Speculation on speculation. The LSA is the best bet as it's the only engine in GM performance lineup that is more powerful than the LS3 but not premium priced like LS7 and LS9. So it could be used on a vehicle priced near the main competiton; GT500.
In any event IF the LSA was put into the Camaro I'd expect actual HP to be a bit higher than the level found in the CTS-V. CTS-V exhaust is toned down becuase it's a Caddy.
However even at 556 HP it trumps the GT500's advertised power already and GM Marketing may choose to leave that figure alone. All speculation at this point.