Via the official PlayStation US Blog:
We can confirm that Gran Turismo 5 will not be available this November 2nd, but the game’s release will be coming this holiday season.
We sincerely apologize to GT fans for the delay, however, creator Kazunori Yamauchi and the team at Polyphony Digital want to make certain they are creating the perfect racing experience, and we are confident that this ambitious game will exceed expectations when it launches.
Expect this delay to apply to all regions around the world – I will update this post as other official sources continue to update for Europe, Asia, and Australia/NZ.
UPDATE: Further confirmation via Polyphony Digital’s JPN website.
UPDATE 2: The delay has been officially confirmed for European regions as well.