Two languages come to mind:

1. Elixir's creator Jose Valim has stated that Elixir is pretty much feature-complete. I think they're potentially going to add some static-typing stuff, but the language is "complete" as far as I can tell.

2. This is going to sound weird, but I think Elm is pretty dang close to complete. Elm 0.19.1 came out years ago, and it's stable as heck. I suspect that Evan has one or two more things up his sleeve before "1.0", and then that will be it forever. The Elm community has a very high standard for quality and stability.