Yeah... These "the sky is falling" what-ifs about FaceId remind me of when TouchId was introduced a few years ago.
Yeah, yeah, but what if, you know, some criminal were to accost you, take your iPhone, and then cut off your thumb with a knife to unlock your phone? What then Apple???
Dollars to donuts that didn't happen even once. People here get so hysterically ridiculous coming up with these insane what-ifs.
I have nothing against the technology behind FaceID, but it's implementation does bring up real concerns. The difference between Passcode, TouchID, and FaceID is that Passcode and TouchID require user interaction by actually physically holding the phone. FaceID doesn't.
As evidenced by this official promotional photo of FaceID. That's a huge security flaw. It's worth being concerned about.