Before people cheer too much, surprisingly works can retroactively be snatched back from the public domain and go back into copyrighted state. The prime example is the movie Metropolis . It became public domain in 1953 but copyright was restored in 1996 only to re-enter the public domain a year ago today.
Just curious...why would anyone here cheer? Have HNers been desperate to launch their own Mickey Mouse novelty tee Etsy stores for years?
The entry of new works into the commons was shut down for a long time, with Disney keeping Mickey under copyright being viewed as the main driver for the lobbying that's kept it closed. We're coming off of two sequential 20-year extensions, and got our first works entering the public domain in the US in 2019, at which point there was a clear deadline for Disney to either get copyright extended again or cede the point.
So Mickey starting to creep into the public domain means the commons probably won't be closed again, since nobody else has as much interest in pushing that as Disney did.