Wouldn't be too weird to think it has something to do with motion control, but I also think it's a purely sales-related trick.
Not only is GT a name that will sell anyway, regardless of the season, it may be smart to keep it away from December, as FF XIII will already sell quite a lot, and the more sold, the more cash sony is giving away. Perhaps they are also hoping that production costs will even decrease some more, so that GT 5 may be launched with a profitable console (which would bring in quite some cash)








