According to PlayStationLifeStyle.net, GT5 might be released 29. December of 2009. This is based on Amazon's official North American listings. Even if this isn't most reliable source, we have to remember that last december Spanish Sony executive accidentally said that GT5 will be released in Christmas 2009. And not to forget the cryptic message in GTPlanet forum. So who knows? Maybe it will come this year...

Related links:

http://playstationlifestyle.net/2009/07/29/gran-turismo-5-gets-holiday-09-release-date/

http://www.techradar.com/news/gaming/gran-turismo-5-dated-for-christmas-489813

http://www.gtplanet.net/gran-turismo-5-rumors-you-can-trust/

"might" lol what have you been smoking ?

Game will come out 2012 ... just so happens the world will end then.

Well who knows...it was first revealed at E3 2006 so it has been in development for at least 3 years. And since then at E3 2009 Kazunori Yamauchi, CEO of Polyphony Digital and creator and producer of GT, said in Eurogamer's interview when asked about release plans that;

"I want to release it as fast as I can, but GT5 for us, when you talk about its status, it's at a point we can release it any time we want, but we can always keep working on it. It's very important for us to make sure everything is done perfectly and everything is done in detail."

So my guess is that the release isn't that far in the future...

NO. As in N-O. Probably next year...

I say its totally possible. but not totally needed. There are enough big ass mutliplatform games coming out on top of some big PS3 exclusives. but it would be awesome. 

The closest you're going to get this year will be the PSP game. Maybe next year.