There are probably many redundancies in face ID, but I wouldn't be surprised if some interesting techniques for fooling it show up.
They seem to work so hard at making sure all their products work well for people various levels of vision problems I have to believe they would've done something. After all even the Apple TV has support for people with total vision loss. I don't see why they'd break their flagship product.
I mean you could just make a setting that ignores whether someone is "looking" at the phone. It would make it a little less secure but at least it would still work.
I have a very hard time believing the rumors that they took touch ID out at the last moment. Maybe when people do teardowns will see some empty space but I figured that something they would've had to lock down early in the year.
I've got to admit I'll miss touch ID. I wonder if it'll ever come back if they figure out a way to get that sensor-under-the-screen thing going, or at this point do they just decide Face ID is good enough and go forward with it alone?
Worst case is that you have to use the passcode and it'll relearn your beardless face.