There is currently no network transparency (thus no xdmcp either) in Wayland. Although the primary developer has left the possibility open that in the future so

There is currently no network transparency (thus no xdmcp either) in Wayland. Although the primary developer has left the possibility open that in the future some remote display support could be added. Of course it is something that could be shimmed into another part of the stack by (NX, VNC, etc) as it has been on Windows for instance. Until either of those happen, X will still happily coexist with Wayland.