https://wccftech.com/apple-might-incorporate-touch-id-in-power-button-on-future-iphone-models/

Apple's new iPad Air 4 features a design similar to the new 'Pro' models. However, instead of Face ID, the iPad features Touch ID embedded in the Power button. While it is a pretty neat spot since the finger first goes naturally to the power button, it seems Apple might adopt the same approach for its future iPhone models. A new Apple patent shows Touch ID in the iPhone's Power button.

The original patent was granted to Apple two years before the iPad Air 4 was launched last year. The patent was then updated to show the lock screen image that resembles that of the iPhone. The Apple patent shows three stages of the Lock Screen authentication. The first stage shows when the iPhone is waiting to be unlocked; the next stage shows when the authentication occurs and the last stage shows when the authentication process is complete.