So why is no one noting that if PC's go ARM, that every single program ever made will break? Nearly 30 years of PC software vanished into thin air...
In many (quite possibly most) cases, it's simply a matter of recompiling, sometimes with minor changes. We're well beyond the days where programmers actually wrote architecture/system-dependent code. Really, the only things that will need major changes should be kernels, device drivers and possibly some libraries.