My guess is that, eventually, OS updates will not work with Intel processors, making all present Macs obsolete. I'm not happy about that!
Its not like that hasn't happened before, it was only a bit over a decade ago, when Apple switched from the Apple/Motorola/IBM PowerPC to Intel. That change was forced on Apple by Motorola's inability to build the newer PowerPC processors and IBM'S disinterest in manufacturing anything other than the very high end
workstation class versions. Switching to ARM processors for the Mac would put Apple back in the processor designer's seat for their entire product line. Remember, the Mac represents barely 10% of Apple's revenue, if that, and is in a global market that is shrinking rather than growing so they need all the edge they can get.
But yes. It may mean current Macs will reach OS and software obsolescence sooner, but I am sure there will be a transition mechanism as there was when Apple switched to Intel. Actually if the developers have been using Apple's free development tools, following the guidelines, and are actively supporting their products, the transition
should be relatively straightforward. If not, then all bets are off. The toughest conversions will be kernel extensions.
It has also occurred to me Apple may continue using Intel processors in the iMac Pro and Mac Pro lines.
