While ARM can be great, I don’t think anyone is entirely writing off x86. Intel owns a lot of fab. And while I don’t get as hyped on it as other people, Intel going hard into RISCV could change the game for ARM (if it was handled in non-typical-Intel way)
But Intel has already threaten MS with a lawsuit if it tries to emulate x86 for its ARM products. Meanwhile when Apple switched from PowerPC to x86 part of the agreement was a share of patents which gave Intel access to the multimedia extensions of the PowerPC (AltiVec?). If this "share" went both ways then Apple might be able to provide x86 translation on their SOC. NOTE: there is no evidence of this anywhere other than what MS was blocked when working on Windows 10 for ARM and the Apple-Intel agreements.
If this does happen I think Intel will not sweat it because it will be only Apple. Apple has no interest in selling CPUs. They want to be able to make severe changes (cut the fat) between revisions and not have people crying about having to update their architecture to support it.
IANAL, but it's been argued here that the x86_64 patents will expire soon (the specification was available in 2000, first processor in 2003). Probably neither Apple or MS will be blocked; MS had a problem earlier since it decided to release while the patents were still in force, rather than wait.
