Earlier quoted context omitted.
He/she is right though, just wait when WebAssembly gets more mature. I bet all those plugins will be back.
Shipping an entire Java/ruby/python/whatever VM with your code doesn't make much sense (not to mention, wasm doesn't have a good GC story). Then there's the DOM API issue. If you aren't making games or crunching big numbers, wasm isn't for you yet. Even so, let's assume wasm added all those features today. History shows it would still be a decade before you could ship to all your users. That may not matter for fancy…
If WebAssembly is good enough as C and C++ target, it is good enough as any of those processors.
As for the potencial of WebAssembly, there are already ongoing efforts to port .NET and Java runtimes to it, and I am looking forward to Adobe porting Flash to it as well.
So it will come, WebAssembly + Canvas + WebGL is already quite usable.