Gary Bernhardt wasn't all that wrong when he mentioned anything that can be written in JavaScript will be written in JavaScript.
This post indeed reminded me of his talk https://www.destroyallsoftware.com/talks/the-birth-and-death...
You can actually use WASM to run your own javascript interpreter and people are already doing that to not be dependent on the interpreter that comes with the browser or wasm runtime (outside the browser). If you are going to run node.js in a wasm runtime, that's what you might want to do. Likewise, if you want to offer a browser IDE for a node.js project, you might want to run node.js in a browser and this is probably what you'd be doing rather than passing through the javascript to the browser javascript interpreter, which lacks most of the node.js API. Just easier that way.
Likewise if you want to run some old internet explorer 10 javascript, packaging up on old version of that as wasm might allow you to do that. The hard part of course would be getting your hands on the source code. But MS might help us out here or somebody might implement something compatible. Very much like is being done with flash.