Wayland does have a TODO file, and I think the bugzilla has many items, too. Many things require further protocol design, and the best way to do that would be to experiment and see how things turn out. If you worked on porting a major toolkit to Wayland, I'm sure you would find lots to do; things that you cannot currently implement due to lack of protocol.
No announcement yet.
Wayland's Weston Now Handles Full-Screen X Windows