NOTE This is not meant to be offensive. It's just an important and personal note.
My worry with WebAssembly is that it won't change the "non-free software automatically being used" scenario.
There was an issue openned against WebAssembly, but it was closed due to inactivity: https://github.com/WebAssembly/design/issues/1011.
Accordingo to Stallman, fostering WebAssembly as it is now doesn't change the already existing problems regarding software freedom, see https://media.libreplanet.org/u/libreplanet/m/free-software-awards-with-richard-stallman-awards-presentation-and-speech/.