IBM still sells CPUs based on the PowerPC (now Power ISA) architecture. AMD doesn’t need to die for x86 to become irrelevant.

But Intel does? Or are you saying x86 becomes irrelevant no matter what?

The latter. I don’t think Intel will survive their spiral without government intervention, the organization is too married to x86. They might transform into something else and keep the name, the same way Nokia stopped being Nokia.