Ruby, and to a large extent Python, started from zero, and gained a ton of traction during the whole Web 2.0 rumble.
Microsoft is starting from a negative perception amongst a lot of engineers, and unless they can provide some sort of killer reason to use .NET technologies -- one that doesn't lock you into their ecosystem -- then I don't see them unseating the established players.
Swift and its descendants will be around as long as Apple is, same story for Java and Android. Ruby/Python/Node will continue on in the Web space, with Go/Rust/C++ duking it out for backend services.
This game changes should Microsoft blow a new market open, though, like Apple and Google did with smartphones.