RISC-V is just an ISA (Instruction Set) that anyone can use, but what people use it in, and how they use it, is not specified and does not have to be open source. Apple could take RISC-V, plop it in their iPhone, and release it tomorrow in a processor that only boots Apple-signed code and requires proprietary firmware without any issue whatsoever. Intel could literally release a Core i5 with a RISC-V instruction set and an Intel ME built-in, no problem.
Where the hope mainly comes from is small chip developers like SiFive, who make many of their drivers and such open-source. But that's only if you buy from vendors like them - if you implement your own RISC-V core, there's no requirement that the drivers or firmware be open-source for it, in any way. You might say that's a missed opportunity. I say RISC-V wouldn't have caught on otherwise.