Earlier this week we told you that The famous Dev Team member known as @MuscleNerd had made some really good progress on an iPhone 3G / 3GS baseband 06.15.00 downgrading solution.
It was a number of big news simply because the iOS 4.1 and iOS 4.2.1 firmware people who upgraded to the present specific iPad baseband to get their iPhones unlocked.
All those users are already stuck on it, without any way to downgrade their iPhone 3g / 3GS to a normal iPhone baseband. As there have been several problems being gone through by people immediately after upgrading, for example — loss of their GPS functionality, it's no doubt a baseband downgrading solution continues to be on their thoughts for a long period.

Downgrade baseband 06.15.00 to 05.13.04 — Release Date

Finally, with respect to a recent twitter update by MuscleNerd the expected 6.15.00 baseband downgrading software will be released this Sunday. You will need to remember that this isn't a verified launch date. This is just a prediction by means of MuscleNerd on as soon as it's going to be released.