The rumor that GT6 was coming sooner, rather than later, started when Italian retailer Multiplayer added a listing for the game, complete with a heretofore unseen box cover, as well as the previously unannounced release date. The listing has subsequently been removed, but the genie may be out of the bottle. Adding a bit of credence to the November launch rumor, we do know that Polyphony is planning some kind of announcement this month, though we don't have any details about it, as yet.
Even if GT6 is going to be ready for this fall, there's some chance that the European and North American game details – launch date included – may differ. However, a pre- Playstation 4 launch of GT6 would seem to be good way to tide over fans of the franchise, while the next-generation console version is being developed (not to mention giving PS3 a big shot in the arm on its way out the door).
Keep an eye out for more news on this front later this month, as well as for updates after the industries E3 convention, in mid-June.