Good point. As Les Whitenaugh pointed out, having a backup copy of your important data is as important as keeping a secure password. Strong authentication may give you a false sense of security, because there are always other things that can go wrong — such as injuring your ‘auth finger’ or having a surgery that makes your eye unrecognisable to the algorithms.
There’s always a trade-off between security and convenience.
As to what happens if your biometric data is leaked, well, that would spell disaster. What could you do? Finger surgery? Eye transplant? I don’t know.
But if anyone else has suggestions, I’d be glad to hear them!