I'm excited for this and eagerly look forward to adopting it in Ember as soon as it's mature, but I'm guessing this is still at least a few years out.
I feel like there may be enough internal pressure from groups in Apple, Google and Microsoft to get DOM integration available, so that they can experiment with compiling the likes of Swift, Dart and C# to it, that it will become a priority once the MVP has shipped.
https://github.com/lukewagner/polyfill-prototype-1
PoC mentioned in the wasm FAQ.