[asow92]

If you're truly worried, I would hold off just a little bit longer. Swift ABI stability is slated for Swift 4.

[stepanhruda]

ABI stability doesn't really matter for users, unless you're using 3rd party pre-compiled libraries. It's mainly an issue for Apple, shipping system libraries.

[mnem]

It's quite important if you're trying to provide libraries for developers to use...

[stepanhruda]

Closed source libraries.

[mozumder]

Is that expected this summer?

[mikeash]

Swift seems to be locked to Apple's yearly release schedule, so we should see prerelease versions of Swift 4 this summer, followed by a public 4.0 release around September.