Sony's chief exectutive in Southern Europe, James Armstrong, may have revealed an approximate release date for Gran Turismo 5 in an interview done with spanish newspaper El Financiero.  Armstrong mentions how the company intends on boosting revenue for next year, and among the things mentioned, he states Gran Turismo 5 as a driving factor, and that it will be due out next Christmas.

So there you have it - Gran Turismo 5, Christmas 2009.  In Europe, at least.