When we see a mule, we'll know for sure. But look at the base weight of a ATS, imagine a 2-door ATS, take out some weight for typical Caddy-type soundproofing and luxury options, and you have it. And then there is the 15% weight reduction mandate.
As for the 450 HP, that's still an estimate for the C7. The Camaro will be less, if for no other reason than a longer exhaust system. But there will still be more HP, and there will still be a weight loss. The future is very bright...