Way to misreport the man's comments
From the blog post this was garnered from:
"No, JS isn’t going away in any foreseeable future. Yes, wasm should relieve JS from having to serve two masters. This is a win-win plan."
From the FAQ it links to:
"No! WebAssembly is designed to be a complement to, not replacement of, JavaScript (JS). While WebAssembly will, over time, allow many languages to be compiled to the Web, JS has an incredible amount of momentum and will remain the single, privileged (as described above) dynamic language of the Web. "
So to say "his" project is to KILL JAVASCRIPT is simply clickbait, inaccurate and frankly godawful journalism.
You also fail to mention that it isn't his project, he just blogged about it. Teams from Mozilla, Google and Microsoft have been collaborating on this - which should be an indication it should be taken seriously.
I think some of Apple's webkit dev's may be on board too, but that seems less certain (its listed in a PR requesting to implement support, from one of their own engineers, but that isn't exactly official confirmation).