[carsongross]

To a large extent it already has, although there are a lot of people fighting a rear-guard effort against it (myself included).

Web assembly may level the playing fields for other languages eventually but it will probably be too late, so javascript will continue to be the native imperative browser language and, in as much as developers care about "one imperative language everywhere" it will be the most obvious option.

My effort (intercooler.js) is to use HTML as the main client side language: it's native and declarative, and lets you take advantage of REST/HATEOAS naturally in a way javascript SPA frameworks don't. By minimizing client side javascript, and since you are always going to be dealing with HTML anyway on the web, you can pick whatever backend technology you like (I like rails) without adding in a new language to the cognitive load of your app.