Your iPhone now has no road back to iOS 8.4.1
The introduction of iOS 9 had its highs and lows. Foremost of the hills was the quick pace of adaption as compared to iOS 8. The bad news, of course, was contained within gremlins and bugs of a v.x.0 release. Now, as we head off to iOS 9.0.2, Apple is not looking back, which isn’t good news for iOS 8.4.1 jailbreakers.
Your iPhone 6s and iPhone 6s Plus will not be able to downgrade back down to iOS 8.4.1 nor can it go to iOS 9.0 if it’s been updated past that threshold. Apple closed the signing window for iOS 8.4.1 to all of itsdevices. It seems that devices from the iPhone 6 generation and older may still access the iOS 9.0 software package, though.
Word was going around of an iOS 8.4.1 jailbreak about to hit the streams, but now, it almost seems for naught. If you fall into the interested party that has an iPhone on iOS 8.4.1, you can definitely hold off on the update. Otherwise, it’s iOS 9.0.1-2 or bust, baby.
Source: Redmond Pie