Today Apple have released the iOS 4.1 beta 2 for iPhone and iPod Touches. But this iOS 4.1 beta 2 can be accessed only by the developers. Only member in the iPhone Developer Standard or Enterprise Program can download it.
The iOS 4.1 beta 2 comes up with a new baseband and so if your iPhone is unlocked now, and still you want the unlock, then it is safe not to update your iPhone to iOS 4.1 beta 2 till an unlock tool is released for it.
Download iOS 4.1 beta 2 from here.