I don’t believe Apple will transition away from x86 anytime soon but for different reasons. They would abandon the pro market if it moved to arm. Most x86 pro applications would have to be rewritten. What would be the incentive for software makers?
Apple might very will be able to bring out a arm stack for consumer market but there is no indication that they can compete with x86 pro or server market.
PPC was niche compared to Intel. So they moved from a dying ecosystem to a thriving one.
If they moved from AMD64 to ARM, they would be doing the opposite. AMD64 is not going anywhere on the desktop and is by far the undisputed performance king. Not to mention how many shops and pro end-users they would instantly lose. The number of developers that run macOS and depend on AMD64 virtual machines must be enormous. Given how much Microsoft is embracing Linux, it would be commercial suicide for Apple to abandon the AMD64 platform since they would be driving all these devs to their competition.
Somewhere in between. First patched, possibly significantly, then recompiled. Unless you have a lot of low level processing in ASM or intrinsics for simd. Then there will be a bit of rewriting.
Apple might very will be able to bring out a arm stack for consumer market but there is no indication that they can compete with x86 pro or server market.