flatpak seems to be adopted by everybody who's not directly affiliated with canonical. Which is only about half of the linux desktop space. Snaps are controversial, but I like them. Currently I'm on Ubuntu with 23.04 and snaps, they work really fine for me. Most of my VMs now use OpenSUSE Tumbleweed with flatpaks though, and that works really nicely as well. 'Normal' users probably don't care, so I'd say that both packaging formats will slowly replace everything else, but only snaps can form a complete system. Flatpaks cannot be used without apt/pacman/rpm/zypper/whatever. Edit: the main benefit of moving to universal repos is consistency. Flatpaks and snaps on ubuntu work exactly the same as snaps and flatpaks on arch, there are no version differences, no differences in dependencies.