The idea of two functional, declarative package/system managers being interoperable is very exciting for me, if it meant I can use full breadth of Nixpkgs with system config declared in Guile. But is that something I can look forward to or is it too much?
I thought Nix was written in C++?
For many Haskellers, I believe the interest stems from how Haskell's "cabal-install" (its closest equivalent to pip, cargo etc) used to be pretty broken. There wasn't universal interest in fixing this, with some insisting that installing dependencies is the job of your distro's package manager, not your language's ecosystem.
Gentoo did an okay job at having coverage of Haskell dependencies, but Nix was the clear leader ever since they could auto-import the hackage database. It's for this sole reason that I moved from Gentoo to Nix.
This pipeline I came through doesn't really exist now, because the Haskell community has endorsed Stackage, and cabal has fixed its core problems by copying the nix solution.
Guix is more elegant in ways such as guile versus nix the dsl, although the haskell underpinning of nix is very useful.
If you're a linux user willing to put in the time and play around then both are perfectly usable as daily drivers but they're both learning experiences as well.
Hard to say which will win out, probably both, with excellent interoperability.
They really are the future of os managment, they simplify abstractions of state and naming