This is historically the kind of thing that people think is very cool and important, but has turned out to not matter at all. "Languages matter" must be the biggest enduring fallacy of computer programming. It has an obvious corollary in believing processor architectures are important.
It matters a whole lot. There's lots of code written in various languages and it's often prohibitive to use it in your own project because making the languages speak with each other (especially if you have performance concerns) is a lot of work. I don't expect WASM to make this trivial, but to say that it doesn't matter is patently wrong.
For instance, memory safety does not really matter so much that people would stop using unsafe languages.