Julia, because fast can be beautiful. I don't know how much it's going to grow but it doesn't look like stalling in the near future. The reason is simple: it fulfills a need no other language does.

I would guess there are some possibilities that could be a menace:

1. Someone manages to convince scientists to use a statically typed language.

2. Computing paradigm changes drastically. Everyone moves to quantum computing or similar.

3. In another 10 years someone learns from the lessons of Julia and improves on them to make a much better language.