The problem with the Camaro is not that it isn't a good car. It's price point is terrible compared to a mustang. Base GT is $32K, base camaro is $37-38K. What does that have to do with the upcoming GT500 though? The new ZL1 is going to be an incredible car, the next GT500 needs to aim at that and higher.
The lower base MSRP is the reason I chose the Mustang over the Camaro. It was hard to justify the extra money for the Camaro at the time(1LE)