You Can Still Test iOS 9
And finally, it's worth noting that you should be able to test drive iOS 9 on your device for a few days, maybe even a few weeks.
Apple should continue signing on its iOS 8.4.1 update for a week or two after the iOS 9 release. If it does, it will leave a nice little loophole open. This loophole will allow users to drop back down to iOS 8.4.1 though nothing older than that.
Look into the downgrade process now because you'll only have a limited amount of time to make your move back down to iOS 8.