If history continues like it has since 1967, the Camaro will be heavier than the Mustang. The 6th gen Camaro will be lighter compared to the 5th gen but don't expect it to be an impressive weight loss. I'm guessing the 6th gen SS will be ~3600 lbs.
2011 Summit White Camaro 1SS/RS
-6.2 LS3, TR6060, 3.45, G80
2004 Black Silverado 1500 2WD Regular Cab, Short Bed
-5.3 LM7, 4L60E, 3.42, G80