Ubuntu is going through a lot of changes now. It will use Unity for the desktop instead of GNOME Shell in the next release i.e. Ubuntu 11.04. However one of the biggest changes is that X.org will be replaced by the Wayland Display Server. This is a huge change and will likely take a few years.
Right now Wayland is not stable enough to replace X.org. However Kristian HÃ¸gsberg, who started the Wayand project, has made a video of Wayland Display Server running in Ubuntu. Here is the video:
Because of the support that Wayland is now getting, development is going ahead quite nicely. There is even a PPA from where you can install it now.
So, if you are the curious type and want to try it out, here is what you need to do:
[Warning: Wayland is in no way ready for normal usage yet. This is only for testing.]
sudo apt-add-repository ppa:xorg-edgers/wayland
sudo apt-get update
sudo apt-get install wayland
To launch Wayland from within X.org, execute the following command: