ARM is already around for decades and has a solid 100% market share in smartphone applications. It also has a very high market share in anything embedded, though there PowerPCs, Mips and others are still surviving.

Not having to pay royalties for the CPU architecture and the architecture being quite extensible has a lot of charm. That is why completely new CPU designs these days start on RISC-V, especially in research. On the other side, there are plenty of ARM-IPs, so unless you are designing your own processor cores, it often is way more efficient for the project just to include the ARM-IP.

I can see RISC-V might make quite an impact on embedded systems short term, but smartphone vendors basically buy what Qualcomm produces. Until they produce an equally powerful RISC-V based design for less money, they will of course stick with the current architecture.

what would be their motivation to switch? They already control everything they need to with Arm. RISC-V would not open any doors for them that are not already opened, as far as I can tell.

It is far easier for them to adjust their existing silicon designs than to adopt an entirely new ISA, given equal gains.

What we're going to see now is 20 years of solid innovation on Arm CPUs from Apple. I don't even like Apple at all, and that is apparent to me.

You base that confident statement on what exactly?

There's no reason for Apple to switch. The amount they might save on license fees wouldn't pay for the transition.