If you’re using logind, this isn’t a problem – if the screenlocker dies, it will be restarted up to 3 times (without revealing screen content), and if it is killed yet once more, your screen just won’t unlock (you can then unlock via a tty by logging into that and using loginctl session-unlock).

If the daemon responsible for this is killed, all your sessions will simply be killed.

In no situation will your screen unlock due to a process being killed (in contrast to the pre-logind world, where, if the screenlocker dies, your screen is free for all, as there the locker is just a fullscreen window)