Gnome shell is going under another change. This one I think is quite possibly the worst thing ever. They're removing the categorised menus in favour of a more "spatial" approach. i.e. the same interface that you have with your Android phone, iPhone, iPad etc.. That is, a grid of icons with all of your applications. I don't think that interface works terribly well. For those interfaces, people then have to have multiple desktops and arrange their applications in some sort of order that makes sense to them. I find myself wanting to yell at them. "My computer is not a phone or tablet! It's meant to be productive!".
So what's Canonical's role in all of this? Canonical is designing Unity. Personally I don't like it terribly much. There are some features I really dig but one of my fundamental problems with it is that it has that same problem that the Unbuntu Netbook Edition (yes, I'm criticizing my favourite interface thus far). It is based on a code base that is glitchy. Ubuntu Netbook Edition had maximus - nice idea. It didn't have the foundations to be stable. Unity is much the same. For their 3d effects, they're relying on Compiz. We've all seen compiz right? The funky spinning cube, wobbly windows etc. I consider it a proof of concept. It got people excited about the desktop all over again. It was a patch though. Consider the first GUI. Any idea what it was called? What it got renamed to? It didn't actually get continued. The people who worked on it took the ideas and what they'd learnt (Most of this work had to do with buffering) and went and developed other Interfaces.
Gnome 3 and KDE have both taken compiz and created their own window managers + compositing managers which suit the user interface.
Of course, this is more likely to come down to ego...