JavaScript has a uniquely privileged position, though. It is the only language you can use to script the browser. As long as that is the case (and browsers are a relevant programming environment), you will always have web developers who know it, either as their primary language or as a secondary one.

Imagine if the only way you could script Linux servers was in Perl -- it's hard to imagine it falling off in popularity the way it did in our universe. Other languages supplanted it because other languages could supplant it.