Since they only rounded to one figure after the decimal place, you could have a range of 3386 to 3414 pounds (using 10.75 to 10.84 lbs per HP).
An LT Camaro with the same engine and transmission combination weighs 3720lbs. So the ATS is at least 300lbs lighter. An SS with a stick is 3850lbs, so we're talking 3550lbs for a fully loaded Camaro with a V8. If some of the features standard on the ATS are not added to the Camaro, you may be looking at sub 3500lbs for a V8 Camaro. Plus I stand by what I said earlier, that the extra doors and glass on the ATS add weight that the Camaro won't have. There will also be significantly less sound deadening material, which isn't light.