Apple’s Swift team plans to have version 3.1 of the programming language ready by spring 2017, then turn its attention to Swift 4, according to a blog post by Ted Kremenek of the Swift team.
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, according to Kremenek. Swift 3.1 is intended to be limited in scope, with the desire to move focus early in 2017 to the development of Swift 4, he adds.
Swift is open source under the Apache license, which says that developers can use the software for any purpose and even distribute modified versions of the programming language without paying royalties to Apple. It's hoped that developers will begin to use Swift for development outside of the Apple ecosystem.