In a rather brief blog post, Mark Shuttleworth announced that Canonical will not continue its investment in Unity anymore.
I’m writing to let you know that we will end our investment in Unity8, the phone and convergence shell. We will shift our default Ubuntu desktop back to GNOME for Ubuntu 18.04 LTS.
This may seem to be out of the blue as Unity 8 was getting new commits almost everyday. I believe the decision to end Unity must have been taken in just last few days.
Gnome Team is happy to get Ubuntu back aboard.
Now why Ubuntu is switching to GNOME desktop, whats wrong with Unity 7? It is a robust and modern desktop environment and has some neat features like Global menu, HUD and so on. Can't Canonical continue to develop Unity 7?
Canonical patches upstream GNOME components to make Unity what it is and when Ubuntu 18.04 comes out, it may have a pure upstream GNOME environment. As mentioned in the blog post, Canonical is now heavily focusing on IoT and cloud segments along with desktop.
Having pure upstream experience could mean less maintenance and patches on the desktop part (unlike Unity). This will allow Canonical to allot more resources IoT and Cloud services. Of course, this is just a theory and we will see actual result when Ubuntu 18.04 goes in development.
In the meantime, if you have a itch to try out latest upstream GNOME on Ubuntu, grab a "Ubuntu Gnome" 17.04 iso from here.