The AI in GT5 sucked. It sucked in GT4, and GT3 as well. Meanwhile, the AI was quite good in F355 Challenge which came out in 1999, before any of these games.
If there is an actual GAMEPLAY related idea that anyone has right now, not graphics, gameplay, that they actually understand how to implement but can't simply because no machine is currently powerful enough to do it then...I'd like to hear about it. I'm pretty sure that doesn't exist. And if it does exist, it would probably take the GDP of three countries to develop it.
The PS4 is going to give you new ways to shoot a guy in the face and share it on YouTube. That's it.