I need to publish an app in September and today, I'm wondering whether or not I should go with Swift 3.
Is it possible to publish an app with todays xcode 8?
Will there be an xcode 8 GM? If yes, when will be it be released?
Can I publish to app store using a beta version of xcode?
Generally not, but unclear for XCode 8. In past beta versions of XCode, they could not submit to app store. ITs also the case that previous beta versions of OS X (now macOS) could also not submit, regardless of version of XCode.
Todays Xcode 8 is beta, you can't publish usaing beta software.
You can publish with Xcode 8 GM when it will be released close to official iOS 10 release.
However in the past, even a GM version of XCode could not submit from a beta version of macOS.
macOS is also a software, so yeah, if you have any combination of softwares that are betas, you can't publish 😉
btw to add to my reply, even with a fresh GM you need to wait for Apple mail before being acceppted by iTunes automatic validation.