Having let slip themselves that the game will support the PlayStation Move peripheral, it seems Sony’s decision to implement motion controls into Gran Turismo 5 is the reason for the game’s lengthy delay
https://kotaku.com/gran-turismo-5-on-the-move-5493293
According to a “source close to Sony”, trade site MCV reports that a decision by Sony to put both motion controls and 3D – which we thought they already had – into the final version of game is the reason Gran Turismo 5, which should already be out by now, is not.
https://kotaku.com/playing-gran-turismo-5-at-ces-in-3d-5444025
Far from ruling this out, Sony says “We will be announcing further details of Gran Turismo 5 in June in Los Angeles during the Electronic Entertainment Expo. Until that time we cannot comment on rumour or speculation.”
So, there’s a good chance that what you just read above, you’ll be reading again in a few weeks time!