If we believe Fleecy then AmigaOS5 will be completely hardware-agnostic and run on everything from x86 to PPC to your gran's microwave and your cellphone.
I don't see any problem with restricting AmigaOS to PPC hardware. Being on x86 didn't do BeOS any good, even when it was free. People downloaded it, played with it on their PC for ten minutes, then rebooted into Windows and forgot about it. This is exactly what would happen to AmigaOS if it went x86.
