Seems CUPS now comes with Zeroconf/Bonjour network printer browsing support included in the upstream tarball. I haven't tried this myself, but presumably CUPS should work on Avahi as well, since we ship a -- these days nearly perfect -- Bonjour compatibility library.
In Fedora Rawhide this functionality seems to be enabled already. Other distibutions, please follow!
Seems at least one good thing came from the recent Apple buyout of CUPS/Easy Software Products: I can now remove one item from my TODO list which has been there for a long time already.