For three years now Canonical has been expressing plans of moving from an X.Org Server to Wayland in a yet-to-be-determined future Ubuntu Linux release. Wayland may finally be ready for some level of use by year's end or H1'2014 while X.Org isn't moving anywhere anytime soon.
The theory that Canonical's rolling their own display server comes from Jono Bacon. Ubuntu's community manager said they don't want to move from the X.Org Server that is quite overweight on features but old and showing its sign of age these days to Wayland, which he says also has too much functionality for their needs. He said last month they'll probably end up rolling their own solution.
This doesn't make any sense at all. Perhaps they will end up writing their own Wayland compositor rather than using the reference Weston implementation or fork it and strip out the features that are uninteresting to them. However, I don't see them at all developing their own display server and protocol from scratch.
Canonical doesn't have the talent in-house to develop their own solution, their graphics/X team is incredibly small and within there is only one developer that does any serious upstream work these days (Maarten on Nouveau), and the design would more or likely be just like Wayland with regards to using the DRM/KMS interfaces, the Linux kernel's input drivers, and other similar design choices.
Not following X11 or Wayland would also mean that Canonical would need to work out support for the tool-kits and other major software to support using their custom display server.
They might be developing their own display server just for phones, TVs, and other unique form factors, but even there it would be surprising. There's already Wayland deployments on some TVs that are shipping plus it's also shown to be useful to Tizen developers for tablets and infotainment/in-vehicle-entertainment systems.
Hopefully in the coming days we'll get clarification out of Canonical about what they're really aiming to do on the display server side.