This rumor reeks of internet forum posters. The rumor of the horsepower bump because of the fact that 5.0 Mustangs are faster in the 1/4 mile is false.
Unless Chevy proves that they are the same old financially stupid company as years past, they will not bump the power in the Camaro before the Corvette. It makes no sense to change the engine in the Corvette now. It also makes no financial sense to change the interior of the Camaro in its 3rd MY run. The cost of changing and retooling is not a smart move when there is no need. They need to refresh the car in 5 year runs like the Mustang in order to make a profit.
Also, Mustang versus Camaro facts.
Both transmission V6 Mustang's are faster than any V6 Camaro.
Automatic 5.0 is faster than L99 Camaro.
Automatic 5.0 is faster than LS3 Camaro.
6 speed manual versus 5.0 versus LS3 Camaro is very close and comes down to driver skill.
Overall, the Mustang is the faster car. Anyone who chooses to use 1 specific test to 'prove' the Camaro is faster and disregard all other heads up results is a GM shill.