non-beta xCode9 release

No, Apple does not release any official or unofficial prediction of future product releases. If past behavior is used as a guide, Xcode 9 will be released when iOS 11 or macOS 10.13 is released, which is typically around September or early October.

FWIW, in past years, developers have got stuck after moving their source code to a new Xcode/compiler beta version in the weeks before an official release, then being unable to deliver a critical update. I would suggest holding off moving any production code to Swift 4 a bit longer for that reason (or use a git branch to separate the two strands of development).

Thank you very much for the response!