The problem is not that you need a unifying language to do this , you already have 2 vhdl and verilog which are mature etc. The problem is and has always been vendors don't want to release their tools. It's like saying only one assembly language should exist. Why? There can be multiple versions of assembly but the vendors of these things need to release a version of llvm or gcc that allows people to build for there devices without having to pay 10000s of dollars to use them.

Players like Xilinx have held out their compliers and instead selling them and using lawsuit to prevent people from reverse engineering there IP. This hasn't stopped people or lesser players like lattice from doing this but it's definitely slowed it down. I think open sourcing or releasing the compliers is just kind of forced because what new company would but a complier if they can get one for free (yosys).