What does it mean ??
Even without the help of Canonical, we could've still install Gnome3 in Ubuntu in the future, but since it's the original Ubuntu developers who knows everything about Ubuntu itself thus them involving in an official repository simply means better compatibility. May not be always true but most of the time, it's true.
For instance, I'm not quite sure how it's now (I don't use Gnome 3 in Ubuntu), but at first it was said not to install Gnome Shell with Unity since they both can easily clash (really, nooooooo :P) thus making a system failure or breaking the Unity desktop in other words. But with the help of the original developers... in the future both Gnome3 and Unity will work hand in hand, finally.
So what happens to "libappindicator"??
Well, according to Akhtar's post in OMGUbuntu, a detecting mechanism will be developed between the two rivals, Ubuntu's appindicator -> Gnome3 appindicator system, thus in the future, thus if Gnome3 is detected ,the Ubuntu OS will take proper action to works seamlessly.
This is a good move actually. Because if we really want to beat Microsoft ... then having a clash between Canonical and Gnome is the last thing that we want. Still this does not mean that now Canonical and Gnome agree with each other... but it's a start, isn't it??.