Oh, it's Hyperion policy never to port to anything that's commonly available, let alone inexpensive. Hell, it took them how many years to port AOS4 even to classic Amigas with PPC accelerators?
I guess at some point OS4 was working on the g4 Mac Mini (only 64mb vram model) but those machines are far too available and inexpensive, so they pulled the plug on that one...
I was going to try it, but my Mini did not have the right video configuration.