Tough question?
Not a tough question at all. PPC in a shape and form that would be interesting to us is dead. X86 would be the best way to go, if desktop is the future of Amiga. But it's also the most difficult, as I have been told (something to do with endians
).
Easier would perhaps be ARM, and lots of things are happening in the ARM world now. The Cortex A8 is being established, the Cortex A9 is growing, and...
"The launch of the Cortex-A15 MPCore processor marks the beginning of an entirely new era for the ARM Partnership." Well, that's no understatement!
Its simplest/lowest performance version (for next-generation smartphones) offers "5x performance improvement over today’s advanced smartphone processors, within a comparable energy footprint", and it scales up to quad-core configurations and speeds of up to 2.5Ghz, clearly breaking the boundaries of traditional applications where ARM has been used, and well into x86 territory.
Some companies are already using ARM in server configurations, something that probably will increase with Cortex-A15. Virtualisation is built right into the server variants of these chips, and they can support up to one terabyte of memory.
http://www.arm.com/about/newsroom/arm-unveils-cortex-a15-mpcore-processor-to-dramatically-accelerate-capabilities.php The road map suggests that 2012 will be when it gets released.
I'd like to see MorphOS ported to ARM!
