As a preface to the comments below, one analyst cited Microsoft's announcement that Windows 8 will not run exclusively on Intel chips but also on ARM--the same chip architecture that powers Apple's iPhone and iPad. So, in a way, Microsoft is already on record with a transition to ARM.
Smart move for Apple vis-a-vis its developers: "This would be, in part, an ecosystem building opportunity. It would be saying to developers that Apple has the opportunity to increase the size of the TAM (Total Available Market) for developers to write for, while also changing the face of computing by bringing key characteristics such as instant-on and long battery life to the notebook clamshell form factor." --Richard Shim, analyst, DisplaySearch.
Apple has switched architectures before but...: "Apple has switched architectures in the past, so it is certainly possible they could switch to ARM. I don't see why they would do it, though. Even with a 64-bit architecture, ARM processors will not offer performance competitive with the high end of Intel's line, so Apple might be sacrificing all of its professional users. ARM may offer some battery life and cost benefits for mainstream laptops, but given that Intel is focusing on these parameters, I don't think the benefits would be sizable. Also, as indicated by its recent 22 [nanometer] announcement, Intel has a manufacturing technology advantage that will prevent ARM from getting very far ahead, if at all. So I am skeptical." --Linley Gwennap, principal analyst, The Linley Group.
It's just a matter of time: "Apple likes vertical integration, has proven ability to migrate software among instruction sets, and can derive adequate performance from non-Intel CPUs. Thus, I think it's only a matter of time before we see Apple computers with keyboards using ARM CPUs. I agree...that it makes sense to wait for the 64-bit ARM instruction set to break cover. My guess is that they'll use a homegrown CPU out of the chute. They've had CPU-development capability long enough in house to have something ready in 2012." --Joseph Byrne, The Linley Group.
Performance, performance, performance: "The concern is performance. Who knows for sure by 2013 what ARM will have? But Intel's 22-nanometer chips will be widely available by then. That will make it tough for other people to compete on a raw performance basis. You can offset by saying we're at the point where there's good-enough computing [so] we don't need that performance. But that's a hard argument to accept because we've said that for years. And yet people keep wanting to buy faster and faster PCs. Oh, and by the way, new software soaks up any extra CPU cycles. That said, over the years [Apple has] done two huge instruction set transitions and they've done them very successfully. So, it's not out of the realm of possibility--in order to give [Apple] a single instruction set in a combined platform. And they could do it in phases, where the MacBook Air stuff goes to iOS and ARM and they keep the higher-end stuff on Intel." --Bob O'Donnell, analyst, IDC
The risk factor: "Has Apple beefed up its chip team? I don't think they have. Besides, silicon is not their forte. I think it would be a strategic mistake. Intel can offer them extremely competitive products, leading-edge process technology, and throwaway prices. So, what's the advantage? There's going to be more risk than upside. If they misexecute on a product line, then the entire product strategy is at risk. And the price-premium argument completely goes away." --Ashok Kumar, analyst, Rodman and Renshaw