It appears that the long in development Gran Turismo 6 is indeed coming to the PlayStation 3 on November 28, despite the strong possibility that the PlayStation 4 will be available by that time. This information comes from the Italian website Multiplayer.com, a retail website that offers the game for preorder. Though the website is in Italian, the game is clearly marked for a November 28, 2013 release date.
Many have speculated that the game would come out as a PlayStation 4 launch title, due to the fact that the game has been delayed for so long and the proximity to the game's release and the expected holiday release timeline the PlayStation 4 is aiming for. However, Michael Denny, an executive for Sony, had slated in the past that the game would appear on the PlayStation 3 in 2013, but did not mention when the game would come out. The game's release in North America could be a different date, and possibly sooner, given that for most game's North America and Japan get a game first, followed by Europe and other regions. Since this news comes from an Italian website, it could only have information on a European release.
This is actually the second website listing Gran Turismo 6 as a PlayStation 3 game. The website Newegg.com had the game listed for the PlayStation 3, but did not list a release date and mysteriously had the game labeled discontinued.
Gran Turismo 6 has yet to be an official release date announcement, so this may all be false information. However, given that time is running low for the PlayStation 3, any games coming to the system will have to be announced sooner rather than later. This information does not also mean that the game could eventually come to the PlayStation 4 at a later date.