well I know its not a virtual case as they made a box art before the PEGI rating and after because I've seen two different boxes, one with just PEGI put on it and one with PEGI 3+
I wasn't aware. That would definitely indicate that it has likely been rated by PEGI then.
If you visit an EU site, the box art has a PEGI rating, but if you go to the US Gran Turismo Site you can see RP (Rating Pending)
And of course this brings up a whole new discussion regarding how PEGI rates games.
The ESRB (US ratings board) is independent of government regulation. They are a voluntary industry ratings system. As such, they can and do hide much of how they rate, who does the ratings, and so forth. However, some supposedly leaked information says that they do not have to see the entire game (not enough time and resources for every game), and the raters often are not playing it themselves, but watching it be played by people that actually have game skills, since the raters are switched frequently and limiting them to only hardcore gamers capable of beating any level of any game is nigh on impossible. Also, ESRB ratings do not apply to any user-created online content, so livery editors, Forza-like storefronts, etc. do not need to be included in a functional manner.
Keep in mind that all that I just described are based on leaks, and any of it can be incorrect, but if true can point to how a rating can be available now.
Does PEGI require the full and completed game? If the version they get lacks, say night or weather effects, or just a bunch of car models, but does contain the entire soundtrack and low res versions of all visuals then it is surely enough to give a rating to. It is a closed course racing game, and as long as it is clear that there is no visible violence to humans, there is no inappropriate advertising imagery (alcohol, tobacco, adult), and the soundtrack is free of offensive lyrics (mild lyrics seem to get a pass) it could easily be reviewed without a final copy being made.
All of that said, we are less than three months away from the JP release date. I would guess they are doing beta testing of everything now as they likely need to go gold by March 1st to meet the physical production and shipping schedules. So, they probably have a test build that can be used by ratings boards.
The ESRB rating may be going slower, or the US version is still a while off. They may also be holding off on an ESRB rating as the ESRB's attempts to provide more information have led to quite a few spoilerish descriptions this past year.