Here's the link for another interview he did on 29th october.

The important part is "Kazunori laughed at the notion of a 2010 release date for Gran Turismo 5, and said it will be released sooner than expected."

http://www.gtplanet.net/kazunori-yamauchis-best-interview-ever/

 That was almost 2 months before the new interview. The fact he went on to say what he did to a car magazine not a games magazine would most likely mean he wouldnt make a joke like that simply because readers of the magazine might not get it. Where as if he said it to a games magazine they would.

Plus also he said the same thing in July

http://www.shacknews.com/onearticle.x/53798

was that a joke to then?

Have you actually read the "interview" from the winner of the GT5 Prologue Middle East Challenge, Ahmed Al Azmi:

-first of all i asked him about the Nurburgring, when its coming ? and what takes it so long? and i told him that alot of people waiting for such a great track.

-K.Y simply said its gonna be in GT5

- then i said GT5!!!! Ohh my God !! thats way to far from now.

- "he laughed" and said : why are you saying that ?

-Me: because of what i know is that the team still didn't think even of targeting a release date for GT5 and to be honest i dont believe GT5 will come before 2 years which is a long time/

-K.Y : "2 years hahaha, no no. dont worry much about that its gonna be sooner than expected"

- Me : any hint about when?

K.Y: he laughed again and said soon.

I don't know the release date but this "interview" is just.. meh..

@ nikkom - it doesn't state anywhere which episode of the magazine the article is from

@ Hyruken -
ok, what he said doesn't deny a 2009 release, it just doesn't confirm it.
It also certainly doesn't deny an early 2010 release, and 2011 is laughable

0811 meaning year 2008 month 11

Why on earth would there be such a big gap between the Prologue and the main game?

because they needed you guys to buy prolog so the could continue to fund the main game 

If this is true that is just insane ... A 5 or 6 year development cycle where the primary benefit is better graphics seems like a waste.

At this point who knows.

Apparently he laughed at the notion of it being out in 2010.

At this point, I'm just ready for the game to come out.