Apple has made available the first Beta release for both iOS 7 and OS X 10.9 Mavericks. iOS 7 beta 1 is available for developers and compatible with iPhone 4/4S/5 and iPod Touch 5th gen. Developers can also get a download code for the first beta of OS X Mavericks by visiting the Dev Center. Both iOS 7 and OS X 10.9 Mavericks will be released to the public this fall.
NOTE: if you don’t want to loose your jailbreak, stay away from beta releases.
