I doubt that this is a hint at DLC, considering the existence of other quotes.Now this is slightly off-topic, but I think Top Gear hinted at GT6 content pre-release. In the first episode of Season 20, there was a Renault hot hatch being tested, and in the test Jeremy started showing some of the computer features. The display looked kinda PD-ish:
And then there was an option to change the internal engine noise to that of another car:
Pretty much all of the options (aside from the bike, obviously) were cars available in the game, some new. I also don't think it was a potential preview of updated sounds, it seems like that would've been announced. Nissan was purchased by Renault, and as we know PD helped with portions of the R35 GT-R's development. It would seem they could've have had something to do with this car, though simply had a much smaller, and less significant role in it's development.
I don't think it's something people should try to grasp at. This is more of an interesting tid-bit than a potential hint, really.
*Edit: I've done some extensive research, and I've been unable to find who developed the computer system.