Crucially, WASM development will be immediately open to all comers. "A W3C Community Group, the WebAssembly CG, open to all," Eich writes. "As you can see from the github logs, WebAssembly has so far been a joint effort among Google, Microsoft, Mozilla, and a few other folks. I'm sorry the work was done via a private github account at first, but that was a temporary measure to help the several big companies reach consensus and buy into the long-term cooperative game that must be played to pull this off."
"WASM should relieve JS from having to serve two masters."
As Eich notes, in the beginning WASM would be developed in close concert with asm.js, but the two would naturally diverge in the future: "A secondary consideration: JS has a few, awkward corners even in its asm.js subset. Finally, once browsers support the WebAssembly syntax natively, JS and wasm can diverge, without introducing unsafe or inappropriate features into JS just for use by compilers sourcing a few radically different programming languages."
JS fans need not be alarmed, however, according to Eich, who continues, "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."