This does make a kind of sense. When Apple had the PowerPC chips it was hard to compare PCs to Macs, and therefore price comparisons were hard to do. Macs were more expensive, but it was hard to quantify just how much more expensive. But, the PowerPC CPUs were made by somebody else, and there were some delays, and no sense of a roadmap, and Apple was left stranded, I believe, on occasion.
When Apple went with Intel, they still didn't have control - but at least they had predictability. At least they thought so. There was the whole Nvidia/Intel thing that Apple had to work around. Plus, Intel may be predictable... but their schedule is not Apple's schedule.
So, I think they want to have the control over the CPU. They can then release new ones when they want. They can go back to making Macs and PCs hard to compare (price-wise). They can pair their CPU with any d*mn GPU set they want. I would predict that Apple will simply pay Intel to Fab the chips designed by ARM. Intel is happy, they get paid to do the profitable work (R&D may be necessary, but it's not a profit centre). And if the design screws up, it's not their problem.
Plus, with a single CPU design that works from workstation systems through on down to iPhones, Apple could unify the OS, or big chunks of it, down the road. When Apple went with Intel, I doubt they ever thought that iOS was going to be this huge.
So - how does a Mac with an ARM chip virtualize a PC? Easy. A 2nd (Intel CPU) on the logic-board. Run Windows/Linux/etc on the Intel chip as a "remote" PC and let OS X connect to it as if it's over a network. You just need enough supporting chipset stuff to make the PC chip happy. It probably won't be great at gaming, but I think Apple doesn't much care about selling to gamers. It would certainly work to support most other VM uses, I would think.
