The current and future crop of American Muscle is looking to be the heaviest yet, with the Mustang weighing in at 3700lbs and change, and the new Challenger and Camaro weighing in the neighborhood of 4000lbs or more. The need for bigger, better and safer cars seems to be driving the weight of cars, as a whole, upwards, which makes it increasingly difficult to maintain decent performance and fuel consumption. If Ford was still making 3100lb Fox body Mustangs, and combined it with the latest in technology, like the 5.4-liter GT500 engine, the resulting vehicle would be quite astounding.
That being said, i have to wonder if the next generation of high-performance cars will steal the thunder from our heavyweights. Cars like the new Hyundai rear-wheel drive concept, the Nissan 350Z, and pocket rockets like the Mitsubishi EVO and Subaru STi all offer 270+ horsepower in a 3100lb or so package. They're small, light, fast and don't have side mirrors that are the size of an 8X10 photo.
I imagine people will always want their V8 engines, the sound of which emanates American muscle. And brand names like Mustang will always be in the minds of the youth with money to burn. On the flip side, the Mustang almost ended up as the first generation Ford Probe. Only time will tell.