From the Swift blog:
On June 2, 2014 at WWDC, the Swift team finally showed you what we had been working on for years. That was a big day with lots of excitement, for us and for developers around the world. Today, we’ve reached the second giant milestone:
Swift version 1.0 is now GM.
You can now submit your apps that use Swift to the App Store.
There are more details on the Swift blog post.