Kidding aside, this doesn't make much business sense. A lot of people buy Macs and run Windows alongside OS X because their work requires Windows. Why would Apple remove that whole segment of the market from their purchasers just to save a few bucks on the chips? I don't think they will.
I also think this is slightly unlikely because it would probably require substantial investment in rewriting a lot of the plumbing for OS X (I don't know much about it).
And even further, why would they work on building their own chips like the A4/5 and then put in the effort to end up using someone else's? If anything, they'll either switch to something else just in the MBA's or you'll see A* chips in there or something.
Keep in mind Microsoft is also working on porting Windows to ARM. Ideally there would be some form of Windows 8 able to run on the new Mac's by the time the architecture transition occurs.
Also, they would have to recompile and test all their existing applications on the ARM architecture. It was a big deal when they switched from PowerPC to Intel.
I guess that this would make sense if they started making laptops running iOS.
I think laptops running iOS are very likely. They saved the company by discovering that appliances for consumers are more profitable than tools for human beings, and this way it doesn't much matter that they've never been able to compete on manufacturing efficiency with commodity computer hardware.
Mostly it bugs me that ARM is seeing more and more use yet I still can't drive up the street and buy one on a motherboard. Freezing out hobbyists is an alarming step backwards for the industry.
Kidding aside, this doesn't make much business sense. A lot of people buy Macs and run Windows alongside OS X because their work requires Windows. Why would Apple remove that whole segment of the market from their purchasers just to save a few bucks on the chips? I don't think they will.
I also think this is slightly unlikely because it would probably require substantial investment in rewriting a lot of the plumbing for OS X (I don't know much about it).
And even further, why would they work on building their own chips like the A4/5 and then put in the effort to end up using someone else's? If anything, they'll either switch to something else just in the MBA's or you'll see A* chips in there or something.