X.org needs a major rework; X11 was a solution for a slightly different set of problems than we have today, but just because it might not be the right specific solution now, does not be something else automatically is or that the fundamental concepts behind X are wrong.
However, even assuming X11 is fundamentally sound, it does not necessarily follow that the best solution is rewriting it. Writing even a good new thing may be more efficient.
If you want the UNIX/Linux world to enjoy the sort of success Windows did in the 95-2005 years its about catering to the centralization, decentralization cycle and having a modern ( ie not X11, but maybe an X12) display solution that is hardware independent, portable, and network transparent absolutely is the thing to do. Plan for 2015 - 2025 rather than trying to implement the ideas and compromises of 1995. Wayland and Mir are backward looking.
I think it's important to remember that MS didn't really know what they should be doing - except for the NT kernel, which I hear is beautiful.
Until XP arrived, desktops used 95, 98 and ME. 98 would last about a day on my box before crashing, while 2000 pretty much just didn't crash on the same hardware. 95 shipped without TCP/IP, and Microsoft pushed their own non-Internet network before they had to give up. XP was not ready for what the net was to become, and suffered inexcusable security problems.
My point is pretty much this: one can not predict the future, and sometimes sloppy work gives good results. Writing good code and providing something which does well at *something* is all anyone can do. Trying to do everything well WILL fail, however.
If Wayland gives better fullscreen video, then I'd like that. Someone running a server won't have to do the same, though - it's not like X11 will disappear at the first sight of Wayland success.