Checking Aptitude, libgtk-3-0 depends on libwayland-client, and Firefox depends on libgtk-3-0 and Orca has libwayland-client and libgtk-3-0 somewhere in its dependency chains. I don't run a full desktop environment, but as these are the only graphical programs I run, I suspect most, if not all, currently maintained GTK applications depend on libwayland-client or some other wayland component and its only a matter of time before Wayland becomes the default across all GTK-based desktops.
Assuming that Orca's compatibility with Qt and less widely used GUI toolkits remains as poor as I've been lead to believe, we might find ourselves racing the clock to fix glitches in Wayland before it fully takes over from whatever its in the process of replacing(I think it's Xorg, but I confess I don't really understand the house of cards that goes into building a Desktop environment even without the extra deck accessibility adds to the mix).
