14 DAY TRIAL // Unity 8 is not ready for regular use, but Canonical is improving it all the time. Users need to know that despite all the important changes and improvements announced for the Unity 8, it won't be terribly different from the current implementation.
One of the things Canonical learned the hard way is the fact that you don't radically change the desktop environment and hope that you made the right call. The company changed the desktop from GNOME 2 to Unity, for reasons that can be explained at a later date, but the change was too sudden. It didn't matter that users had some time to get used to Unity before the official launch. Most of them hated Canonical for that decision, and many still do.
A lot of the Ubuntu users are now used to Unity and the way it works. To be fair, the developers have greatly improved the desktop environment over the years, and it's now pretty much complete. The only thing that Canonical needs right now is to replace Unity 7 with an alien Unity 8 and some users in the community think that it's going to be a big change.
Unity 8 will be an evolution, but not in the way people think
Mark Shuttleworth has recently said that Canonical is looking to avoid another GNOME / Unity switch that would alienate a part of the community. The Ubuntu developers are working to keep that balance, so they will not be very far away from Unity 7, even some visual changes will be made.
A number of previews for Unity 8 have already hit the internet, but they are pretty far away from the finite product. Some users even said that they don't want to have an interface on the desktop that resembles the one on the phone. It means that users don't really know what to expect from Unity 8, although the Ubuntu devs have said time and again that it's not going to be a major difference.
Unity 8 is right now scheduled to make a default appearance in Ubuntu 16.04 LTS, which will launch in April 2016, but it's not a firm commitment and it might be launched even later. In the meantime, users will benefit from improvements for Unity 7, which are done all the time, including for Ubuntu 15.04, which will launch in just a few weeks on April 23.
Update:
I wrote this after I saw that many users are confused about what Unity 8 will look like. Some say they don't want a phone as their desktop, which means Ubuntu devs weren't very clear on this aspect, and some users got the wrong idea.