Long ago, the iPhone Dev-team didn't announce any news regarding downgrade baseband 6.15.00 to 5.13.04 to fix GPS problem on iPhone 3GS / 3G. For who don't know, GPS stuck on iPhone 3GS, 3G after upgrading their basebands to iPad baseband 6.15.00 to unlock iPhone 3GS / 3G with Ultrasn0w.
Someone asked MusclNerd on Twitter if there's any updates about downgrade 6.15.00 to fix GPS problem, MuslcNerd replied him that he won't release downgrade 6.15.00 baseband before iOS 5 public release which expected to be between the end of September to start of October.
Someone asking MuscleNerd : men any news about 06:15 downgrade, i need my nike+GpsSo that, it's highly expected that downgrade 6.15.00 baseband to fix GPS problem is almost completed, but as usual all hackers are holding their major hacks, jailbreaks and unlocks after iOS 5 release to keep them away from Apple hands.
MuscleNerd replying: there's a good reason to not release anything like downgrade that before iOS5 (though sometimes I think I overthink it!)
Update: Now you can make iPhone official factory unlock, you can check the details from here