ARM can't compete with x86 on desktop. IMHO choosing ARM would be a suicide. It doesn't fix any problem, it doesn't bring any advantage to customers, it's yet another hard to find hardware platform. If MorphOS was going to migrate to other cpu it should be x86 because you can buy x86 machines everywhere, there's enough variety. I'm not interested in vapour cpus with inflated benchmarks. ARMs performance sucks. 1Ghz ARM cpus are slower than all PPC equivalents. There's no ARM machine that can compete with a QuadG5 machine in price/performance right now.
If we switched to other architecture it should be x86 (it's cheap, it has a wide variety of models from low consumption to high performance, it's easy to find, it won't dissapear)