How long have we been hearing about the possibility of a Gran Turismo for the PSP? We can't pin it down exactly, but our estimate is: a long time.
But it seems we have an unofficial release confirmation from an inside source at Sony Computer Entertainment Europe. According to Agent-X at HipHopGamerShow , the source said- "I actually know a lot, but I will only tell you this one even though I am not suppose to, Gran Turismo will be making its way to the PSP this year." In addition, he said that Yamauchi didn't initially like the idea of porting his legendary franchise to the handheld – presumably due to the amount of gimping that would have to take place – but in the end, he decided it'd be a good idea. At the previous link, you can read the IM conversation that led to this discovery, but of course, until we see something concrete from Sony, we have to label this as rumor. The idea of a GT coming for the PSP in 2009 isn't too far-fetched; Sony has said multiple times this that this could be "the year of the PSP," what with all the great software on tap. If the inside information is true, it's likely we'll see the announcement at E3, where it has been said that many more PSP titles will be unveiled.
We know that PSP owners have been waiting for a Gran Turismo for quite some time, so it'd be awesome news if it finally dropped later this year.