I'm not trying to suggest that Apple's ARM chips are magically better because they're designed by Apple. Rather that the x86 architecture is obviously very long in the tooth and now would be a great time to switch to a far more modern architecture especially in light of this steady stream of vulnerabilities and defects that keep being found in x86.
I'm sure ARM64 isn't perfect but I've yet to learn of something as severe as this, or Spectre, or Meltdown.
Almost all of these exploits are due to the out-of-order/speculative execution.. which is incredibly complicated. There is no reason to believe that an out of order architecture that has not been hardened is any better at defense here than x86 - Just that as a minority architecture, it's still less profitable to target for exploitation. I have very little faith that the Apple ARM chips do better here without extensive exploit attempts made...
Speculative vulnerabilities have virtually nothing to do with the instruction set. Changing the language of the processor has little to do with how the processor works under the hood, especially for fundamental technologies like speculative execution.
Also, as a corollary, speaking the same language doesn’t mean every vulnerability is shared. AMD does not seem affected by Downfall, for instance.
I'm sure ARM64 isn't perfect but I've yet to learn of something as severe as this, or Spectre, or Meltdown.