There's a small hitch. Unless China is allowed to directly pilfer ARM IP, they're going to pull off a RISC-V (or homegrown ISA) transition at the drop of a hat. And if American phone manufacturers are intent on diversifying, they very well might too; there's little forcing you to use ARM as your RISC ISA on Android or iOS. Competitive ARM cores don't grow on trees, and the licensing fee does't make it very attractive to compete unless you have a de-facto ISA license like Apple or Nvidia. And both of those companies have dabbled in RISC-V too. The intent to usurp ARM's throne has been clear ever since Nvidia was blocked from outright buying it in it's entirety.
Look at it this way; Apple can design their own cores whether they use ARM or RISC-V, and control the software from top to bottom either way. Nvidia's already shipping RISC-V microcontrollers to cut down on manufacturing margins, and without better options the rest of the world might follow. ARM's dominance is only possible if better RISC options don't exist; and for anyone that's not ARM the idea of IP serfdom sounds awful.
Look at it this way; Apple can design their own cores whether they use ARM or RISC-V, and control the software from top to bottom either way. Nvidia's already shipping RISC-V microcontrollers to cut down on manufacturing margins, and without better options the rest of the world might follow. ARM's dominance is only possible if better RISC options don't exist; and for anyone that's not ARM the idea of IP serfdom sounds awful.