Writing for Ars Technica, Andrew Cunningham interviewed Craig Federighi on Swift going open source and how Apple is approaching open development:

The Swift team will be developing completely in the open on GitHub,” Federighi told Ars. “As they’re working day-to-day and making modifications to the language, including their work on Swift 3.0, all of that is going to be happening out in the open on GitHub.”

So instead of getting a big Swift 3.0 info dump at WWDC 2016 in the summer and then digging into the Xcode betas and adapting, developers can already find an “evolution document” on the Swift site that maps out where the language is headed in its next major version.