I don't think Apple can develop an iOS version that runs faster and better than previous version on the same iDevice. iOS 11 is the new baseline. Thay can say whathever they want about shifting to performance and stability but that doesn't mean you will have a faster iOS according to Apple standards, iOS hasn't introduce real "significant features" in years (calling emojis a significant feature is lame) and every update is already announced as the best ios version yet, however every year performance is degraded if you don't buy the latest device. They already sell billions of devices with this formula and if most of consumers are more than happy with Apple and issues only exists in macrumors forums, why change your budiness model? They won't, it is just PR because is what some customers need to hear right now.