Right, it's not CPU arch, but there's a much higher chance of having the entire thing open arch if the CPU is. I expect the probability of reaching a de-facto "standard" SoC to be much higher in RISC-V and I'll take the pain of being the early adopter.
I have a lot of sympathy but fear that RISC-V will lead to even more fragmentation than we see with ARM - eg proprietary extensions. PC standardisation is largely due to the level of control that a couple of dominant vendors have not due to the status of the IP in the core.
If risc-v ends up fragmented then it will eventually evolve to a couple main vendors having a good level of compatibility between them and then the market will just agree to include those. Whatever the majority uses.