HAL is in maintenance mode - no new features are added. All future development focuses on Software/DeviceKit-disks, Software/DeviceKit-power, NetworkManager, PulseAudio, udev, ...
See http://www.freedesktop.org/wiki/Software/hal for more info
X.org input device detection needs migration to libudev
Xorg uses HAL on *BSD, Linux, Solaris, and OpenSolaris.
udev appears to be Linux only, so would not be a usable replacement.
For a future libudev migration, here are some questions and answers that may come up.
Patch sent to xorg-devel for comments,
Since there is no suitable cross-platform replacement for HAL, we agreed
last year that we'd have to return to platform-specific code for replacing
HAL's functions, as described on http://www.x.org/wiki/XorgHAL
Xorg 1.8 includes the xorg.conf.d replacement for HAL .fdi configuration
for all platforms, and the udev implementation of the device discovery/
hotplug notification replacement for Linux platforms.
Other platforms still need to implement their platform-specific replacements
for the HAL device discovery & hotplug notification functionality.
Removing from blocker list - the dependency is optional, and having it for
the platforms that haven't yet provided an alternative is not going to stop
the release. We still need to work on it, and will probably remove the
option someday, but not this release.
I'm going to call this one as FIXED, since it only has an obvious replacement on Linux (TTBOMK), where we preferentially use udev anyway.