In a blog post by Alexander Mikhaylenko’s it was announced that GNOME 42 is going to ship with the options between a light and dark theme. Based on the article it looks like the GNOME team is going to be taking heavy inspiration from the recent implementation of this feature in Elementary OS.
" The idea is more or less exactly same as what elementary OS is doing: there’s a system preference, a tri-state with values:
prefer-light . All 3 are just hints — apps are free to follow or not follow them as appropriate. The
prefer-dark values are exposed in settings, while the
prefer-light value is reserved for future use."
Future development of this feature hopes to accomplish a switch in gnome-shell, day/night scheduling, synchronizing wallpaper with the preference, and full support among all applications.
For more information check out the official post on blog.gnome.com.