That's a joke, but I think Windows vs. Linux is the right reference frame here, assuming that RISC-V proves out. Those who want to roll their own and control their own destiny may go with RISC-V, while those who want a packaged solution will go ARM. And ARM will have to get better to compete.
Western Digital has gone with RISC-V for a controller, because Western Digital is the kind of company that wants to commoditize its inputs so it can sell a packaged solution to its customers as cheaply as possible. I can also see Amazon or Google finding uses for RISC-V in their data centers.
Phones ... I'm not so sure. Maybe Apple could go that way, as they're vertically integrated and already make their Ax chips in house. But the Android OEMs wouldn't unless Google leads the way.