Coming when? I have to build applications in the here and now — not the mythical time and place were 99% of my users have a web browser that supports WebAssembly. I mean seriously, that could take 5+ years. When it happens, there will be a new Babel plugin that will compile ES2020 down to WebAssembly. Done.
“SPAs are far more complicated to write than traditional server-based applications, eating up more…
Josh Vander Berg

While we’re waiting for WebAssembly, I strongly recommend using transpiled languages. There are lots of wonderful choices. They even make writing SPAs much less complicated than in JS with Angular, Ember, React, Backbone, etc. Many companies and developers use transpiled languages to great success. (And I’m not talking about CoffeeScript nor TypeScript nor Babel. I’m talking about using real languages like Smalltalk, Python, Clojure, Dart, Haxe and Scala.)

When WebAssembly finally arrives, we’ll be able to choose from a number of superior languages. The good news is, if you choose transpiled Smalltalk, Python, Clojure, et cetera now, your language investment will be preserved in 5+ years.