The news on the net is it's set for a 15th September release in Japan.
Other info is that SCEJ will release the PSP Value Pack in "Ceramic White" containging the PlayStation Portable, AC adaptor, battery pack, Memory Stick Duo (32MB), headphones with remote control, pouch & hand strap in one box.
System software for PSP will also be updated to version 2.00 on July 27th on the SCEI official website. With this update, the various additional features such as installation of the internet browser which allows users to have the internet access available to make the PSP a more attractive entertainment system.