If we're talking dream cars don't forget the new Gulf GT40
Although considerably slower than cars such as the R390, dont forget the Panoz, the old GT40 and the Jaguar XJ220 race car.
The Nissan R90CP (which is arguably cooler than the slightly dumpy looking R89C)was tested for inclusion. One would expect that the 2004 Audi R8 team Goh will be included as a result of it being both Japanese run and this years winner. It is also of note that versions of the R8 and the Bently speed 8 have featured in cheaply made games like R: racing evolution, which would tend to indicate that there is no real problem getting the licences.
Another possible is the Japanese Dome Kondo Mugen, as I believe that it ran without Namco sponsorship this year.
In regard to the GTS category, heres hoping that PD have done a racing version of the Saleen S7 that has already been confirmed so that we can spank the GTS-R and C5R