NixOS is currently in its release schedule, so the picture is a bit more complicated than usual. 10/12 months of the year, the package will not be backported, and you need to wait for the next release to get it from stable (unless someone makes a good case for backporting it).
During the release period, it depends on exactly where in the schedule you add the package. If your package is merged today I think it would just barely still end up in 24.11, but end of next week you’d have to wait until 25.05. The release schedule issue will tell you exactly what happens when: Release Schedule for 24.11 · Issue #339153 · NixOS/nixpkgs · GitHub