Mere mortals use interface, they like ubuntu because some ubuntu-only options and free cd's, because it's popular, not because it's opensource or just "good".
So, it's time to think about middleware, improve everything that is common for all distros and improve standard, force every distro to be visually interoperable. Nobody cares about dpkg or rpm, kernel version or canonical. Users care about what they use. They use desktop. They like Gnome? Improve it, make it same everywhere.
Why should I care about Ubuntu or Opensuse if I use Gnome on both? Where's the difference? That's the issue community should resolve and it's going on and on for last 5 years - we've got middleware everywhere - in packaging, sound, KDE, Gnome etc.
I guess Canonical realizes, that one time usability war will come to the end and this time has come. Not it must create something that will force it's old users to use new versions. That's why they are so crazy about Mir and pushing Ubuntu-only software. That's the reason.