GNOME is going to change the way extensions are loaded in GNOME 45, and that’s going to be a bit of a nuisance for both users and developers.
Extensions that target older GNOME versions will not work in GNOME 45. Likewise, extensions that are adapted to work with GNOME 45 will not work in older versions.
You can still support more than one GNOME version, but you will have to upload different versions to extensions.gnome.org for pre- and post-45 support.
I guess the upgrade from GNOME 44 to 45 is going to be even more of a hassle than GNOME upgrades normally are due to broken extensions. Outstanding.