I'm amazed at how good GT PSP looks, the video's I've seen so far look brilliant for a hand held system. I think you can be pretty sure that if they have the license for those cars in GT PSP you'll see them in GT 5 too.
PD are the ones to push every litre of awesomness from any console. The processor in the PSP is pretty beefy, but Sony only unlocked it recently, and PD are the ones to take advantage. Many devs wouldn't put the time into harnessing it as it's a slightly undesirable product (compared to the DS).
Although they do cheat sometimes, most of the screenshots are renders (like the ones above). Only difference in-game would probably be less Anti-Aliasing, which I couldn't care less about
This is very likely to be in GT5, I must say. But it's late in development that they announce it, eh?
Regarding the Porsche licence, I remember seeing an ad for GTHD a few years back and it did have a white Porsche in it. You have to remember, aftert the whole Citroen thing, Motor companies are more than likely diving into the GT5 bin. Best ad ever is to race a near perfect virtual recreation of a car with the companies badge on it. PD win, the industries win, and we win