Successor languages usually take a long time. Some of them are made by people who are bad at estimates and will grandly tell you that next year they will have finished the language, but that's just because they actually have no idea. In reality it's typically ballpark ten years.

Most programming languages "go nowhere" in the sense that they never end up used for lots of real world projects - but they can have interesting and useful ideas which inspire future languages.

Google writes a tremendous amount of new code. You can reap a large portion of the benefits by using Rust for new code.

> Carbon seems to have gone nowhere.

At least as far as public info goes it's still being worked on. The GitHub repo [0] has pretty consistent activity and some recent-ish talks [1], one of which says that they are considering a 0.1 release "early next year".

[0]: https://github.com/carbon-language/carbon-lang

[1]: https://github.com/carbon-language/carbon-lang#2026

Go is good enough for many tasks. Google wrote that as a replacement for C++ too. I guess Carbon is intended to be more for systems programming? Go had that intent initially, but soon realized that's not a good fit.