They have, HLSL has practically won the shading language wars in the games industry, even on consoles, the Playstation and Switch shading languages are heavily inspired on HLSL.
Also as I noted on another comment, Khronos is basically leaving to Microsoft HLSL as de facto shading language for Vulkan, as they don't have monetary resources, nor anyone else, interested in improving GLSL as a language.
However, as per MSL and HLSL 2021 improvements, alongside SYCL and CUDA, eventually C++ will get the spot, and I doubt this is an area where any of the wannabe C++ replacements can do better.
Note that WGSL is closer to Rust than C++--syntactically speaking anyway--and it's pretty much guaranteed to get traction as it'll be the only way to talk to the GPU using a modern API on the Web.
Also as I noted on another comment, Khronos is basically leaving to Microsoft HLSL as de facto shading language for Vulkan, as they don't have monetary resources, nor anyone else, interested in improving GLSL as a language.
However, as per MSL and HLSL 2021 improvements, alongside SYCL and CUDA, eventually C++ will get the spot, and I doubt this is an area where any of the wannabe C++ replacements can do better.