I tend to think JavaScript is the "next Java": It's nobody's favorite language, but it's the one that many, many, many projects and businesses settle on as a compromise on popularity, availability of talent, quality of tooling, options for deployment, etc.

And, I would disagree with you on Java being a "much better designed language". I enjoy coding in JavaScript a lot more than Java and always have (even though neither is my favorite), and historic Java had tons of misfeatures, too. Both have evolved in very good directions, but I think JavaScript is evolving faster and in more interesting ways, partly because of its history of being an open platform vs. Java's Sun->Oracle guided path.

Both also followed some dead ends...JavaScript, in particular, has always been a mess of warring factions, and the uncomfortable bolted-on feeling of some of the Java-like things it borrowed in the early days is particularly weird feeling in today's language. Coding in JavaScript feels like coding in three or four different languages. But, the thing as a whole isn't bad at all. It's extremely powerful and has become extremely concise in recent years (which has always been the biggest turn off for me with Java...so many damned lines of code, I just can't see the forest for all the trees).

Edit: I agree that WebAssembly is going to shake things up, but it'll probably be many years before any language is as widespread as JavaScript on the web.