I actually never took PPC seriously for Amiga. Commodore never produced models with PPC, so from a purist point of view, they were not Amiga, and I'm pretty sure that they didn't start getting produced until after the Amiga market was commercially dead from my point of view. They always seemed to be more of a retro add-on. Kind of like the products from Individual Computers.
By the time I had even heard of them, it was pretty clear that the PPC wasn't going anywhere on the desktop.
So, for me, the original Amiga was a 68k processor. Anything else is an attempt to bring back Amiga on a new platform. If I was going to try to bring back Amiga on a new platform, there are two obvious choices. x86 and ARM. x86 is being attempted by AROS and CUSA. x86 is an obvious choice because it has so much market momentem.
ARM on the other hand has started to be VERY interesting. Computers passed the 'good enough' stage a few years ago. So, we are now in the 'reduce resources' stage. ARM is doing amazing things in this area. I wouldn't count Intel out yet, but I don't see ARM going away soon. With it's mass production, and continued development, it is a legitimate target for future systems.
So, from my perspective, ARM is a more legitimate target than PPC ever was.