Re AmigaOS being tied to a specific hardware. AmigaOne and OS4 were always going to be transitional. Compatibility had to be ensured for the existing PPC (603/4) Amiga cards. I have read nothing that says AmigaOS will forever use PPC.
I thought the ultimate plan was for the OS to merge with the DE and become scalable and platform-agnostic, using Tao's virtual processor technology. This is where Amiga-powered mobile phones start to make sense - digital convergence, with Amiga content on all the various devices.