Mobile OS's have far passed peak change. I think iOS 7 was peak change. Where it went to the transparent UI, swipe up bar etc. Everything since has been a tweak. The next future of "big change" will come in VR/AR || carOS when each OS update dramatically makes the experience better and more efficient. I doubt we will see much in phone OS space in the new few years as VR/AR/ CarOS ramps up.