The lowRISC team at Cambridge are working on exactly that. However, there's a lot that needs to be finalized in the privileged ISA before it can be implemented in a board. Manufacturing a bunch of boards that require a non-standard toolchain wouldn't be very useful.

That being said, you can already use a RISC-V processor by programming the RTL onto an FPGA board. The Zedboard and ZC706 are both officially supported. Though both of these boards are pretty expensive.