I never considered this! But it's fun to think about!
I'm a bit naive about the environments languages have to run in... but if we have a web app framework in Swift, Servers in swift (as mentioned in comments above), and iOS in swift, doesn't that make Swift a JS replacement too?
JavaScript's domain is mostly client side web browser scripting, and no language is close to throwing it off its throne. So no, JavaScript will always have its place.
I'm a bit naive about the environments languages have to run in... but if we have a web app framework in Swift, Servers in swift (as mentioned in comments above), and iOS in swift, doesn't that make Swift a JS replacement too?