> Or perhaps AMD will let x86 fade away.

I agree with what you write otherwise, but not this. Why would AMD "let x86 fade away"? They are one of the two oligolistic CPU providers of the x86 ecosystem which is worth zillions. Why should they throw that away in order to become yet another provider of ARM (or RISC-V or whatnot) CPUs? I think that as long as the x86 market remains healthy, and AMD is in a position to compete in that market, they will continue doing so.

> oligolistic

I meant to write "oligopolistic", of course.