Keep in mind the current Zeta architecture was developed (starting in '99) for introduction in 2006 and was a flexible platform able to be built in varying wheelbases and overall lengths. The Gen-5 Camaro version was about the smallest version built. So its emphasis, and therefore structure, was intended for generally larger versions than the Camaro...up to 118" WB (6" more than Camaro).
Going to the new-Gen smaller Alpha platform will, all by itself, save some weight BEFORE implementing "new age" weight-conscious measures I'm sure we'll see more of with CAFE '16 ever-present. As suggested by the Caddie ATS data, V6 Camaro models around 3,400 lbs. sound likely...and very encouraging.