I agree with the evolutionary approach.
Kind of like what Audi did from the first gen to second gen TT. The first one was such a hit, so they didn't mess *too* much with the overall form- just some modern styling cues and body lines here and there.
That said, GM's got their work cut out for them. Like a previous poster mentioned, Ford's going to come out swinging. Has anybody seen the 2013 Mustang on their site? Sweet baby jesus...