Unless they are focused on decreasing bloat, I don't think that this will happen. There are lots of utilities and other software that still uses GTK2. I doubt that GIMP was the last tool left to prevent dropping GTK2. I found this from ArchLinux, search for "gtk 2":
Plus you can search for "GTK 2" dependencies. Some sites seem hopeful to move to GTK 4, while others wish they could move to 3, and some talk about upcoming 5.
https://wiki.archlinux.org/title/Uniform_look_for_Qt_and_GTK...
Plus you can search for "GTK 2" dependencies. Some sites seem hopeful to move to GTK 4, while others wish they could move to 3, and some talk about upcoming 5.