Okay, so maybe the game is done. Maybe it's just a technical thing…
GTPlanet has been delving into the Gran Turismo 5 delay issue in an attempt to uncover a root cause. As it turns out, and as a moderator at the Blu-Ray.com forums stated, this is all due to the recent hacking/pirating snafu, which resulted in SDK moderation and restriction for the first time. This in turn caused problems with GT5:
"Like I said it is manufacturing issues. I had it confirmed today.
The problem arose when SCE mandated SDK 350 on all games releasing after after October, GT5 was about to go gold running on SDK 341, but it has been delayed by around a week so that they can update to SDK 350. This has caused a big headache for the manufacturing side, given how big this game is missing the gold date by even a week can cause a months worth of delay as slots are already taken up at this time of year for Blu-ray movies and such. So Sony had to find a 3 week slot big enough to make 7m+ copies of this and get them shipped out.
This follows hot on the heels of the news that Polyphony Digital missed their production window by a mere three days . Firmware update 3.50 for the PlayStation 3 is a good deal more secure than 3.41 and simply put, distributing a GT5 for the new version insures it can't be pirated. Well, for the time being, at any rate. So for all you who desperately attempt to defend software piracy with double-speak by saying it doesn't really hurt anyone, this delay may be just for you.