I'm not really sure wasm is meant to compete with JS like that though?
To me the main benefits of wasm are that you can
* make web pages with languages besides JS
* do lower level things not possible with JS (low latency real time games?)
If you already know JS well and want to make a normal website I don't think you need WASM necessarily although it will enable those who don't know JS or want to use JS to make them too.
Once they add GC, threads, polymorphic inline cache, and some sort of stdlib, it will be possible to have popular scripting languages run in the browser without the current problems of download size for the runtime and performance.
So, it may not be completely intentional, but WASM does have roadmap items that may end up competing with JS. WASM starts to look more like a general purpose VM over time.
To me the main benefits of wasm are that you can * make web pages with languages besides JS * do lower level things not possible with JS (low latency real time games?)
If you already know JS well and want to make a normal website I don't think you need WASM necessarily although it will enable those who don't know JS or want to use JS to make them too.