Important: This project is in the early stages of development. It is not yet ready for production use, but it is ready for contributions. It is scheduled to be part of the Swift 3 release.
Swift 3.0 https://github.com/apple/swift-evolution
Portability: Make Swift available on other platforms and ensure that one can write portable Swift code that works properly on all of those platforms.
Now, it's looks like a good time to start developing PureSwift, but as I see it will be same as 0.9 cocos2d in good old times, so final stable and powerful version of new cocos2d we will get around 2017.. in a best case.