MuscleNerd, the well known iPhone hacker of the iPhone Dev Team, has just announced via twitter that he has made great progress on the 3G/3GS 6.15.00 baseband downgrade. This means that those who are officially unlocked and upgraded to 6.15.00 for the unlock, can downgrade back to 5.13.04, which will allow for both an unlock via ultrasn0w and GPS working!

Made great progress yesterday on downgrade from BB 06.15 (for 3G/3GS owners who got officially unlocked). All the pieces are there :)

He then further clarified his previous tweet by stating that his downgrading solution will allow an iPhone 3GS or iPhone 3G to downgrade from 06.15.00 to a baseband prior to 05.13.04. It is without a doubt that this is some great news for those who are stuck on the 06.15.00 and do not have functioning GPS! Although there was no timeline associated with a public release of the 06.15.00 baseband downgrade, I am sure we can expect something in the near future. Hopefully this will turn in to a release.

We will keep you updated.