They already have automated Haskell packages from cabal, it shouldn't be hard to integrate cargo with nix once it's more stable.

You wouldn't even require upstream NixOS packages, just place built cargo packages in the nix store, using it like a cache. Then upstream NixOS channels could start accumulating cargo packages, making cargo dependency "builds" faster.

Yeah, nix does look pretty awesome and aware of (even actively designed for )both the system administration and development use cases. If it becomes the native package manager for some popular operating systems, I may have to eat my words about language-specific solutions.