Apple reiterates plans for Swift 3.1 release in Spring 2017, offers new details on changes
As it originally announced back in July, Apple has confirmed that it plans to release Swift 3.1 sometime during the Spring of 2017. Following the Swift 3.1 release, focus will shift to Swift 4.
Swift 3.1 is intended to be source compatible with Swift 3.0. It will contain a few additive enhancements to the core language as well as improvements to the Swift Package Manager, Swift on Linux, and general quality improvements to the compiler and Standard Library.
Swift 3.1 is intended to be released in the spring of 2017.