I agree that ARM would be a good platform for AmigaOS to run upon.
And many ARM SoCs are very Amiga-like in their methodology, having dedicated co-processors for specific functions (video decode, video encode, security acceleration, graphics, audio, etc) besides the ARM core(s).
In addition they are fairly cheap for even a fairly powerful SoC. They aren't on quad-core Intel i7 territory, but they're not half bad.
The Raspberry Pi will be a $35 computer (with ethernet, etc, the $25 variant is rather too limiting). However it is only an 800MHz ARM11 - two generations behind the ARM Cortex A9 used within something like the Panda board. The A9 is competitive on a clock by clock basis with Intel's Atom cores.
And at some point there will be quad-A9s (NVIDIA Kal-El, and others), and then A15s at 2.5GHz. By then we are at the 'enough CPU power' stage for a majority of users. And a dual-A15 at 2.5GHz will beat out a 1GHz PowerPC 460 by a long way.
By the time AmigaOS (or Aros) was fully ported, with the necessary drivers, we would certainly be into A15 systems. A core requirement would be sharing the development of the hardware with other projects (e.g., next generation Pandaboard, Raspberry Pi, etc).
