Speculating about what Apple's going to do is a great way to be wrong but I don't really see it. In both of their CPU migrations the switch was to substantially more powerful CPUs. I can see them making more 'pro' iOS devices, Macs with ARMs as coprocessors, etc. Ditching Intel altogether? I can't think of ways the advantages would outweigh the disadvantages.
My guess is that the CPU "leap" will be in power efficiency rather than raw performance. My guess is that the returns for each jump in CPU power these days isn't helping the vast majority of users, but they certainly care about battery life.
