WebAssembly is pretty much going to be mapped to Asm.js initially. Most of the features it's getting that asm.js doesn't have yet are future asm.js features which wasm is also to be mapped too. This includes things like pthreads, SIMD and the ability to support GC languages.

Note: a future version of WebAssembly may be able to use the browser GC.

Yes, that's what I meant.