It is only natural that in some point, mobile phones CPUs will be based on x86/x64 architecture - in fact, I think the only thing that separates us from having a Core i3 or i5 cell-phone is probably batteries...
As soon as there will be a breakthrough with mobile power sources (which - as far as I know - is a field which progresses VERY slow), I'm more than certain that we'll see a major switch from ARM to x86 based CPUs.