I have posted a blog post to Swift.org that documents the official release process for Swift 2.2:
https://swift.org/blog/swift-2-2-release-process/
Please feel free to email this list or me directly questions about the process. In a nutshell:
Swift 2.2 is a mostly source-compatible release with Swift 2.1.
Swift 2.2 officially branches from master on January 13.
The exact release date is TBD, but Swift 2.2 will be in convergence for a few months and become final sometime in March to May of 2016.
Please see the post for more details.
Cheers,
Ted