The performance per watt point is a more than fair argument. It also cuts both ways. If Apple decides ARM is still the performance per watt leader in 20 years, there's a good chance they'll still be using it. If any other processor tech reaches a better spot, they have the expertise and the semi-closed ecosystem to switch processors quicker than pretty much anyone else in most of the spaces into which they sell. It's something they've not only done multiple times, but done well and are known for doing well.
100%. Look what happened with GPUs and Imagination. Personally I think CPUs and ISA will become less important as more functions are passed to special purpose engines. Perhaps RISC-V extensions might be a trigger but I suspect Arm will offer Apple whatever they want to keep them (both on the ability to add new extensions and on price - if they are paying anything at all at the moment!)
