Indeed there can be more than one lingua-franca, much as Fortran and Pascal shared the native machine with C. But they all have in common that they added littl

Indeed there can be more than one lingua-franca, much as Fortran and Pascal shared the native machine with C. But they all have in common that they added little by way of run-time dependencies, and a web lingua franca would also need this property. But on the web, the basic "built-in" run-time is much richer than was available to those languages. It includes the DOM and many other things. JavaScript already exposes all those things, and no more, so I think it is ideally placed to become (remain) the dominant lingua franca. So even if the WASM world is multi-lingual, expect APIs to be described in JS terms, maybe with some kind of backward-compatible type decoration thrown in.