I have for a while suspected that Apple plans to move their entire line of computers to the ARM processor. After all, the shift from PPC to x86 was in part motivated by power use (http://en.wikipedia.org/wiki/Apple_Intel_transition#Reasons) and ARM is much better than x86 in this department (in spite of Intel's attempt at lower-power CPUs). What is currently missing are high-performance ARM processors, but with Cortex A9, ARM processors will start to compete with x86 even in this area.

More important is that Apple can license ARM and include it in their own SoCs, which isn't (AFAIK) possible with x86. The recent acquirements and hirings hint that Applw is, indeed, planning this. SoCs have their greatest benefit in small portable devices (like iPhone or iPod), but it will also enable Apple to make thinner laptops and desktops with smaller form factor (or integrated in keyboards or screens).

Apple may even do like Marvell and license just the instruction set and build their own ARM processor cores. This way, Apple won't have to wait for others to plug the performance gap. There is nothing in the ARM design that precludes high-performance designs. In fact, I think it is easier to make a high-performance ARM than a high-performance x86 -- especially if you want to keep power usage low.