My vote would be for effort on PPC os4 to cease and for a renewed back porting effort made to 68xxxx.
The reason: installed user base. I would also Persue partnerships with the guys making vampire / appolo so that cheap upgrades for amigas were available with real OS functionality to follow.
Amiga OS is never going to make it in its own right - porting to x86 is somthing I would have advocated for back when the decision to go ppc was made but not now.
I think a real resurgence of the scene could be made to happen if cheap accelerators were avaialable along with os upgrades to match.
People would be able to upgrade existing hardware and eventually new hardware would get released - similar to fpga projects that give us compatible, but upgraded features.