GT4 is rumored to have between 500 & 1000 cars.
One of the reasons GT3 had so few cars compared to GT2 was Polyphony's(sp?) modeling process. In GT2, a car took maybe a day to render, but in GT3 it took an average of a week/car.
Regarding the exclusive licensing NFS had on certain manufacturers, I think that's over with. At least with one or two.
The game developer has to pay the manufacturer to include their cars; not the other way around.
Oh....and the Grand Canyon course -
