Now that it has been brought up, is there any reason not to go x86 anymore?
Sure: it's boring, ugly crap, and they'd lose a lot of performance relative to modern-ish PPC CPUs by having to run all the existing PPC software in emulation. Additionally, AROS already exists, so it's not like the world needs another of it.
Now, as to all the other questionable design decisions (no Altivec? Seriously? And tacking on useless Xena stuff
again? And making a new board when they don't even properly support half the existing ones?) I got nothin'.