The instruction set is already reduced (hense RISC) to the bare minimum for the two important profiles: microcontrolers and linux machines. Microcontrollers will be 32-bit and will nessesarliy have a different tool-chain from 64 bit computers as they won't be running Linux. The only question is will most Linux machines use vector. That is probably a yes. X-86 and ARM are allready fragmented and the software ecosystem survived. Nobody is adding custom instruction to a reduced instuction set just for the sake of it. Also, as RISC-V machines will only run on Linux for at least the next few years, all the software and compilers are open already. So there is no way for a single vendor to lock in the ecosystem.