The day has come!
Yesterday I dropped the superfluous hal dependency from gparted, today I uploaded gdm to stop using hal for getting the keyboard layout and use libxklavier instead.
I also applied Julian Cristau’s udevified X.org branch to our xorg-edgers packages into my halsectomy PPA, created some udev rules for udev-based X.org input detection (1, 2), and off we go: that was the last hal reverse dependency. My system now fully boots and works without hal.