The Camaro has to downsize. It is already heavier and just larger overall than the Mustang. There are some pretty solid rumors that the Mustang is going to downsize a fairly substantial amount, if the Camaro barley downsizes there is going to be a large discrepancy between the two. The lighter and more nimble Mustang would own the Camaro in every aspect, except for interior room. You don't buy a sports car for interior room..
We'll see what happens in time..