Apple has placed iOS 7.1 beta up on their developer center, which means registered developers can download it now and start testing it for use with their apps. A matching version of iOS beta for Apple TV is also there, as is Xcode 5.1 developer preview (DP).
Since the content of the iOS 7 beta is covered by Apple's non-disclosure agreement (NDA), we can't report on what, if any, new features it contains. However, if you're not a developer we can and will caution you to stay away from betas. They're not released to the public because they're not meant for the public. As to general availability, it will depend entirely on how many betas Apple decides to release. Typically Apple releases a few, which means anywhere from one to three months.
If you are a developer, go get it!
Source: iOS Dev Center