I don't love that a post from July talked about stabilizing and releasing 2.4 "in the next few weeks", and now it's September with still no release. OTOH, the list of milestone issues is pretty short:

https://github.com/NixOS/nix/issues?q=is%3Aopen+is%3Aissue+m...

I expect the delay is mostly due to all this debate raging about `nix shell` naming and semantics: https://github.com/NixOS/nix/issues/4715