Jason Snell, in an editorial for Macworld:
Okay, so the 680×0 era lasted 10 years. The PowerPC era lasted 12 years. We’re now almost 11 years into the Intel era. All things being equal, the time seems right for a fourth processor transition, and soon.
It could definitely happen. I don’t want to say that it won’t, because Apple’s desire to chart its own course and not be beholden to other companies for key parts of its products is well known. Having proven itself a capable chip designer with the A series, Apple could very well dump Intel and strike out on its own.
But I don’t think Apple will.
Snell’s reasons are manifold, but the biggest is cost: rewriting the components of MacOS that aren’t already forked for ARM would likely not be trivial, especially for a company that seems to dedicate fewer engineering resources towards the Mac.
David Sparks disagrees with Snell:
I can’t help but think that Apple’s tendency to want to control everything would probably be enough for them to commit resources to switching to ARM. If Apple designs their own silicon, they’ll never rely on Intel again. Also, with the ever increasing race for better battery life, I’d expect Apple could make a MacBook that runs a very long time on an ARM-based chip. Jason Snell’s a pretty smart guy and been around this racket much longer than I but I wouldn’t be surprised if Apple does bring ARM to the Mac at some point, even if it is just the lower-powered, super-long battery MacBooks.
There’s potentially a different avenue that Apple could take that would allow them some independence from Intel while also not requiring them to recompile MacOS for ARM: they could start developing their own x86 processors. It’s likely to cost far more than switching to ARM on the Mac, but it would give Apple the flexibility to build processors that meet their requirements for high-performance hardware well into the future.