Yes, you should master JavaScript -- it's used all over the web and people will continue using it that way. But I disagree it's making all other languages irrelevant and that it's a "game changer". Devices are not going to be coded in JS any time soon (the runtime isn't robust enough and the language is not designed to be used that way). Yes, people may use asm.js more and more to convert bigger programs to run on the web, which is super cool, but asm.js isn't JavaScript.

So master JavaScript, but then learn Rust, Elixir, Go, Haskell, and Lisp, too. These are as much "game changers" as anything else.