This is a huge shift if it happens. X has been synonymous with GUIs on unix for more than 20 years, and has accumulated all the attendant baggage (both good and bad).

There are also some big consequences for the linux landscape. The first and obvious one is that if other distros don't imitate Ubuntu they will drift farther apart. People complain about Ubuntu going their own way now, image what it will be like if they're on Wayland+Unity and others stick to X+Base Gnome.

Another, subtler consequence of Shuttleworth's announcement is the message it sends to graphics card vendors (well, NVIDIA really). Wayland is dependent on the newest linux graphics stack, very much by design. But that stack is relatively new (e.g. kernel mode setting) and nvidia never updated their driver architecture to match. I assume this will force their hand because Ubuntu is too big to ignore.