A Way to Go Back to iOS 8
You can count on there being a way to go back to iOS 8.4.1 after the iOS 9 release arrives for iPhone, iPad and iPod touch.
Apple will almost certainly continue signing off on its last iOS 8 build in the days after the iOS 9 release date. If this happens, and we suspect that it will, it will leave a loophole open. This loophole will allow you to go back to iOS 8.4.1 if the iOS 9 isn't up to snuff.
Don't count on the loophole being open forever though. Apple typically stops signing within one to two weeks after a release so don't expect to be able to go back to iOS 8 in November or December. You'll need to act pretty quick.