Just like the headphone jack, right? Because Apple’s not stubborn and it totally makes sense for them to backtrack on device features like that...
Honestly, if FaceID works as promised, why would you even need TouchID? There’s no added benefit unless FaceID is a total failure, and even if it is (which I wouldn’t bet on), Apple would probably throw money at fixing its issues rather than roll back their devices to what they are already treating as an inferior solution.
I'm not so sure the usability of Face ID will be accepted by everyone. It clearly has problems where you want to momentarily wake the device to see notifications, and without putting your face in the field of view, for example. The more I thought about this I decided to let the tens of millions of early adopters give it a go, and maybe Apple will make changes, or add Touch ID along with it for the next go-around.