So far, but judging by what Canonical has done over the last couple years that might not be the case for much longer.
Might, but as long as it isn't that way, it's still a GNU/Linux flavor. Personally, the only divergence I think they shouldn't do (not that I directly support the others, but I don't think they are problematic) is Mir.
As for the others, you might like or dislike some (I like upstart, though I think systemd has superseded it, and I frankly can't stand Unity), but none of them harm anyone because they don't spread the fragmentation.
I love the claims of backwards compatibility. Please. I can't run firefox 4 on ubuntu that came out in 2009 and they care about some motif app made in 1990. who the f** needs to run a motif app while using the latest version of x.org. name me one person. the idea is so retarded that my mind explodes. the "we would break the x rendering protocol if we change x too much" was and is a huge canard. what they are doing with xwayland, they could have done years ago. namely to run x apps with a new architecture side by side. and yet the biggest excuse when the Fresco came out was that "what would happen to all those poor x11 app"
With DRI3, which parts of X.org can be thrown out?
Is DRI(1) thrown out yet?
Any other part that can be thrown out?
I hope they put X.org on a diet, and really cut it down and trim it down and make it light and make it maintainable. But its hard with so much legacy and backwards compatibility.
That's what's been happening for a long time now, and it's also one of the reason Wayland is being written in the first place.
Many of the former "core" features of X have moved out either into the Kernel, separate libraries and specialized clients, leaving X(org)
as a very superfluous and largely inefficient IPC mechanism.