The Wayland support for UI interaction and EGL context creation has been implemented in https://developer.blender.org/D6567. Everything related to EGL context creation (onscreen / offscreen) and keyboard + mouse interaction with the UI (but mouse wrap) is suppose to work. It is ready for general testing (cmake option -DWITH_GHOST_WAYLAND=ON).
Some features, like setting the cursor position or accessing absolute screen coordinates, are not available on Wayland by design. Some other features, such as drag&drop / copy&paste, window decorations and relative mouse movements, haven’t been implemented yet. I intend to do this after the basic Wayland support has been merged.
I would be happy to get some feedback on this (@ideasman42, @julianeisel, @brecht).