Yeah, there are two categories of cars, 'Premium', and 'Standard'.
Standard are cars which were taken from the previous GT games. Retextured, and tweaked for GT5, which will include some degree of damage (like scratches).
Premium cars are modeled from scratch. Full damage is included in these cars because each fender has been modeled so that GT's engine can incorporate full on body damage.
The game would've come out around 2030 if 1000+ cars had been modeled from scratch
. GT6 will probably have more premium cars because PD will work from GT5's engine. Plus, it'll take half the time it took GT5 to develop since they have GT5's engine to work off of. Hope that helps