Yes, cars and track detail are dependent on each other. GT's use of 2d trees/no skid marks/2d details, are dependent on how detailed the car models are. Having super detailed cars+16 on the track has it stands presently (2d effects) is perfectly acceptable and within reason. But if they were suddenly drop the cars down to say Gt4 level, they would have to
A. increase the #of cars on the track by 30+ or so.
B. put the extra resources into the track models.
If they did nether a lot of power would go to waste, and it would make the absence of 3d details/skid marks all the more apparent. Lesser games seem to follow plan B where a good amount of detail goes into the tracks, though their car models are completely next-gen in design as well.
GT apparently decided take detail away from the track and put it into the cars (I like GT's plan better) along with more cars on the track as well. Numbers and graphics are usually performance killers but GT pulls it off better then everyone else.
Since we have not seen any crazily apparent track side detail increase (all 2d trees being replaced with 3d/skid marks etc) They are either
A. 30+ cars added when standard(gt4 level detail) cars are used.
B. There is parity between all cars and the models are of the same detail as the one in GT5p and this new demo, barring the damage differences. 👍
C. A good amount of power is wasted, and we have last gen car models on a pseudo next gen track, with no 3d track side detail or skid marks along with all the other complaints, sound/AI etc..👎
Obviously, plan C is not PD's style. But if the cars had lowered their details something would need to be compensated.
All evidence points to Plan B, since we have not seen a dramatic increase in track side detail. So throw this up there with the other arguments where all the cars contain a dashboard view/are highly detailed.