iOS 7 Gold Master now available for developers
Apple has finished work on iOS 7 which is a pretty big (and long overdue) redesign of the iOS software, but that doesn't mean the work is done. iOS 7 has been given the label of Gold Master, which means it is out of the beta stages, but it still needs one last round of testing by developers; and, more importantly, developers need to test out app updates with the finished iOS software.
The GM seed version is 11A465, and it has been released to developers. Most of the time, the Gold Master version of Apple software is what will ship when it is officially released, but sometimes Apple may tweak something here and there. If you are a developer, you can grab the update from Apple's iOS Dev Center, and get to work.
If you're not a developer, we would suggest waiting it out for the official release of the iOS 7 software, which is scheduled for September 18th. It may be safe to install it early, but there have been reports that Apple has been bricking devices that are running iOS 7, but aren't tied to a developer account. So, really the risk is yours.
source: iOS Dev Center