Be careful not to conflate web programming with plain-old JavaScript the language. A lot of the horrible bugs in web programming come from the massive complexit

Be careful not to conflate web programming with plain-old JavaScript the language. A lot of the horrible bugs in web programming come from the massive complexity and size related to web browsers, the DOM, and over-engineered frameworks. If we're talking about streamlined, embeddable JavaScript, we're not bringing the web and all those bloated frameworks. You are right that those writing web apps won't necessarily be good at embedded systems, especially since (for now), they will have to also separate web APIs from JS-the-language and will not have the APIs they are used to. But those who survive the transition process will likely pick up better habits. I suspect the APIs and usage will end up looking a lot like the Lua sphere, though perhaps more fragmented since none of JavaScript engines have anything remotely resembling compatible C API interfaces.