You don't need to stay in C. You can pop through to Rust or Golang or what have you.
Both of those are comparable to C and compiled. Rust is a bit lower level, Golang a bit closer to C++.
Go is the odd one in the list, you might as well say that one should write an external function in Java and call that from Ruby (which would be fair if Ruby would already run on the JVM, e.g. in case of TruffleRuby).
Go has nothing at all to do with C++, C++ is a low level language, and an expressive one at that. Go is neither of those, it is managed and not good at expressiveness (by design).
There's no need to wait for TruffleRuby (unless you want to).
Ruby is great for developers of all skill to learn and be productive.
Rust is fast as the devil but you have to be a damn good coder to learn it. Even then I doubt you can be as productive managing memory all the damn time. It's a low-level language great at low-level things.
Ruby is a great option for Shopify. Rust is a great option for Firefox's Servo (though that project failed so maybe not).