In a recent interview IGN had with Kazunori Yamauchi, the creator of the Gran Turismo franchise, talks about upcoming DLC arriving at roughly every 2 months.
IGN:Can you talk about how much you've been able to update and improve Gran Turismo 5 since the game first launched?
Kazunori Yamauchi:It's been about a year since we've released the game and in the interim we've had about 15 updates that were performed on the game. These set up the basic platform for the system. Now that we have that out of the way, we're ready to release more expansions and content to add to the game. I think that will include cars and trucks that we'll be releasing maybe once every two months or so from here on out. What we do from here on is also really dependent on the reaction of the users to this first DLC that we just released because this is the first one. Now we have the feedback from our customers and we'll see how that will affect what we will do from here.