Just learn whatever you currently need. If you know a few paradigms, learning a new language of the same paradigm is easy-peasy and can be done rather quickly (well at least being be productive with it, doing stuff idiomatically often takes a little bit longer).

That said, Rust IMO is a language that makes sense to learn anyway, since it also teaches you to program in a nicer way (not just true for Rust, there are other languages that have this effect as well, such as Haskell etc. generally languages that introduce something really new (i.e. a new paradigm)). Generally it makes sense to learn multiple languages, as each brings you new ideas. But on the other hand it makes sense to learn one language really well (I'd recommend that being Rust, as it can cover so many use-cases and is generally designed nicely (it fills a sweet spot between mutability and functional programming IMHO).