See the full post for more ARM Mac speculation
"If (or, more likely, when) the Mac switches to Axx chips, the change won’t be instantaneous. Some Macs will become powered by Apple’s home-grown CPU chips, others, like the Mac Pro, will remain on x86 processors. And thus we’ll have a fork of macOS. Two forks, actually: A sliding break as the transition progressively moves from low end machines up the product line, and then a permanent “fork ceiling” that separates the extreme-end Mac Pro from its lower-powered siblings.
As for the software transition, Apple has proved many times that it could easily handle processor changes, the latest example being the PowerPC to Intel 2006 move."Apple: Macintosh Forks | Monday Note