Since Swift is open source most of the changes in the new major version were already known before WWDC. Having said that, Apple did made a few interesting changes (mostly naming) for the new Swift release. Click this one to read more.
Source: Swift 3 – Ole Begemann
Version 3.0 of Swift is expected later this year. Although there is no final version yet and the language is still under development there are some known “source breaking” changes. This post reviews some of the most important ones and will help you prepare for the 3.0 release.
Source: What’s new in Swift 3.0: learn all the changes in one place – Hacking with Swift