There are a couple of additional comments about the future of GT5 and Gran Turismo as a whole in the Famitsu.com version of the interview.
The print version did not make any mention of a date for GT5's late December update. In the Famitsu.com version, Yamauchi says the update will be available around the 20th or so (that's not an exact time frame, but it does sound like we won't have to wait until the very end of the month).
In the full version of the interview, Yamauchi was asked if the possibility exists for past courses like New York City, Seattle, Grand Canyon and El Capitan to be revived in the future. He responded in the affirmative -- the possibility exists .
Yamauchi was also asked if he wants to make the next Gran Turismo on PlayStation 3. Responded Yamauchi, "We'll probably end up making it for PlayStation 3. However, I still don't know. I don't know what kind of hardware will come out, after all."
Remember Gran Turismo Kids/Boys? (If you don't, read this IGNPS2 article). Famitsu bought up the game now six years after Yamauchi first mentioned it at the Gran Turismo 4 completion party. Is Yamauchi thinking about making a Gran Turismo Kids based off GT5?
"I'd really like to do it," replied Yamauchi. "I get asked this question by the European press too. The problem is that I don't have the time for it. In a sense, PSP's Gran Turismo was made to be enjoyed by kids. GT5 is online, and requires a certain level of communication skills, so it would perhaps be tough for kids. I'd like current kids to play it after they've grown up a bit."