I agree that displacing (or even supplementing) JavaScript is much more difficult than it seems. However, I don’t think that the state of JavaScript today is captured by the “800 pound gorilla” analogy. If it was, we wouldn’t see so much turnover in frameworks. We wouldn’t have jQuery replaced by Angular and then replaced by React and Vue, etc., all with barely a shudder.

It’s also interesting that you link to an excellent article by Eric Elliott, because he was one of the first voices I heard extolling WebAssembly. While defending the value of JavaScript, he also said (a few years ago) “WebAssembly is an open invitation to developers building future programming languages.”

I don’t think JavaScript is in any danger in the next decade. It is currently the only option for browser development, and it will remain the most mature option. But it will be interesting to see if a-non-JavaScript-based client framework emerges to compete with what we have today. The future will be interesting!