I think the switch to Unity is beginning to pay off.
Other distros that decided to write their own flavour of the new Gnome are going to get increasingly bogged-down with that. Hopefully they might be able to combine a few of those projects and at least one will remain sustainable and go in a good direction. It's a bit of a gamble though and there is no certainty in what they are doing.
Ubuntu is primarily a gateway project to help people migrate away from non-Gnu&Linux. As such it is still highly successful. Even if a lot of people are still jumping-ship it doesn't really hurt Ubuntu all that much. Most of those people are likely to be working upstream in projects such as LibreOffice and other programs that are often used in Ubuntu. By working upstream they help more than one distro.
Unity is becoming increasingly useful to power-users so many of those people will probably return but with new-found (or rediscovered) skills and interests and hopefully some interesting new ideas too.
I wasn't a huge fan of Unity at the start but i had a feeling that things would go this way. Fortunately for me i am really happy with Unity in the 12.04 so i was able to stick with the 10.04 and then smoothly 'upgrade' (actually did a fresh reinstall on most machines) from one LTS to the next.
So, for me it's all been a bit of a storm in a tea-cup.