If you could believe in the Mir specifications on the Ubuntu Wiki it seems we'll be getting a single display server across all form factors this time 2014. I'm not privy to the inner workings of X, Wayland or even Mir but it seems Wayland has been around much longer than a year and it's still not "good enough" to replace X. At least not completely.
If my memory hasn't failed me, Btrfs had a goal of "feature complete" in a year and it's been much more than "a year" yet Btrfs is still not considered feature complete although it's usable by the brave of heart.
But maybe there's something Canonical knows that other experienced developers don't. We'll see next year how things turn out. I'm just getting a "premonition" that Mir is either going to be very buggy, or very feature incomplete in a year's time. Take your pick.