I don't know if packages should necessarily be moved out of nixpkgs since I doubt most people who don't use nix would want to maintain flake.nix in their project, nor would users want to have 30+ flakes in their inputs. However, I can see a good case for separating the package definitions from the nixos modules and the stdlib (mkDerivation, stdenv, etc). Maybe there could be a flake for each.

As for keeping up with PRs and other responsibilities, that seems to be one of the stated goals of the this new Nix Team. I guess we'll see how they intend to handle this soon.