I don't see Go as a panacea for opening up libraries for use. You're still going to see languages that can export C interfaces for that. It's going to be C, C++, and Rust that are likely to persist as the languages of choice for massively consumable libraries. As long as they can export a C interface, you can get low (or no) overhead interop. Go's biggest disadvantage is that it ships by default with a runtime.

I hope I'm understanding your comment correctly.