Do you think that, for example, someday a distro like Arch Linux will switch to Flatpak ?
I think that is highly unlikely that it would switch wholly to containerized packages. At least in the immediate future. In the far distant future, anything could happen.
However, we already have support for flatpaks if you would like to use them.
I know, but I’m old school, and I hope that Arch Linux/EndeavourOS will stay like they are now.