"So far in the Gran Turismo series," explained Yamauchi, "we haven't had cars crash or overturn. We believed expressing this properly to be more difficult than actually making [the cars] race. In addition to properly replicating the underside of the car, when a collision occurs we'd have to have proper shape changes based on proper physical calculations. In Gran Turismo 5, we'd like to definitely add this element. We believe it will be a big theme."
Crashing isn't all Polyphony is considering for GT5. Apparently, the limited EyeToy support offered in the Nike limited edition version of Gran Turismo 4 could hint at some features from GT5. Mentioning his interest in the mere idea of a game making use of images from a camera, Yamauchi states that he'd like to make
use of image recognition in GT5. He doesn't go into specifics beyond this, unfortunately.
If GT5 does feature image recognition,
it most likely won't be through the EyeToy.-
IGN