The plan is to avoid duplication, and to keep the Xorg extension and base X libs in sync. They have been updated every time the Xorg extension has.
The next update, Xorg 7.5, will come with TC 3.0, because many features depend on the newer kernel.
What do you mean by incomplete? If xcb, I consider that bloat (Python, added size for little benefits), and will do without it as long as possible.