Ubuntu founder Mark Shuttleworth wrote a blog post this week contemplating the possibility of making Ubuntu's new Unity shell work on the Wayland display system, with the aim of eventually shipping Wayland as Ubuntu's standard display manager. A transition of such enormous scope isn't going to happen in the near future, but it certainly can't hurt to start thinking about it now.
The X Window System (X11) is a cornerstone of graphical Linux computing. It is a display server that is responsible for showing graphics on the screen and mediating user input. The ubiquitous X.org implementation of the X Window System is included in all mainstream desktop Linux distributions. The problem with this venerable component of the Linux technology stack is that it was created in the 80s and hasn't been able to shed the superfluous accoutrements of yesteryear computing.