I think Fil-C ABI implemented by all of C, Rust, and Zig is the future. But that would need some sort of stability for interoperation, and stabilizing ABI takes time: Rust still doesn't have one (while Swift spent enormous amount of effort to have one). Experimental implementation is probably still worth doing.
It currently is at least associated with C in the sense that it takes C code as an input. But yes, I would be very happy to see its approach applied to more languages.