As you well know, many distributions have adopted the Wayland graphical protocol to replace the old X. But some of them have resisted, or have taken a step back and have returned to X, as is the case with Ubuntu. But, it seems that in less than two months the new version Ubuntu 21.04 that could change everything, since it will try with Wayland.
Ubuntu 21.04 Hirsute Hippo will arrive loaded with new features, in order to be able to adjust them all and polish them to create a slightly more stable distro when the LTS arrives. Therefore, it is the ideal time to get back Wayland again and see if it already stays or if they remove it again in some other future version of the Canonical distro. In principle, it would come to stay ...
Wayland is already the present, and also the future of the Linux desktop, to leave the old X behind. Thus, Ubuntu 21.04 would follow in the footsteps of Fedora, CentOS and RHEL 8, which are prepared for Wayland in their GNOME version.
In the case of Ubuntu, there was an attempt four years ago, just leaving the graphical Unity shell to go back to pure GNOME. But the truth is that it did not go very well and in Ubuntu 18.04 LTS reverted to X.Org sessions. And the biggest drawback is the portability of the software, since it needs modifications to work on it.
It is true that Wayland was an alternative option for those users who wanted it, but not an default selection as expected to be on Ubuntu 21.04. Although not for all graphics cards and only for GNOME, the other flavors will have to be seen later ...
Sebastien Bacher, one of the developers of this distro, assured that «In the Ubuntu 17.10 cycle we tested Wayland as the default session, but we didn't feel sure at the time that it was ready for an LTS. […] We think now is the right time to try again, you should give us plenty of time before the next LTS to get the right feedback and fix the issues. […] NVIDIA users will continue to use Xorg by default for now, but hopefully that situation will be resolved before LTS.«.
Remember NVIDIA is one of the main problems of the adoption of Wayland.