In addition to the March 25 release date for Japan more Gran Turismo 5 details are leaking out.
Game Star’s Gran Turismo 5 product page lists features such as direct YouTube replay uploading and connectivity to Gran Turismo for PSP. If you have both games, you can transfer car data. Gran Turismo 5 will have over 950 cars and twenty locations to drive in. When you factor variations there are more than 70 courses to race on.
The last thing Sony Computer Entertainment America said something about Gran Turimso 5 scheduling was they were targeting summer 2010.