14 DAY TRIAL // Canonical is hard at work to release Unity 8 for the desktop users and they are focusing on all the essential features that you would expect to find, but some of the less important ones, like the ability to install themes, won't be available right from the start.
One of the things that people love to do with their Linux installations is to customize them. Users install themes, icons, transformation packs, all kinds of utilities, and who knows what else. The result is that many of these OSes feel unique, and they usually are. The problem with Unity 8 is that users won't be able to do all of these, at least not from the start.
Many users are expecting Unity 8 on the desktop in order to test it and even use it as the default desktop environment, but Canonical is now focusing on providing the best and the most stable experience possible. Stuff like icons or themes is not exactly high on their list of priorities. They are not doing anything actively against theming, but it won't work without their effort.
Unity 8 is a package deal with Mir
When Unity 8 eventually lands, it will do so accompanied by a ton of other technologies, such as Mir and Snappy packages. It's easy to understand why regular themes won't work with the new desktop environment, at least not right away.
Canonical knows that theming is an important part of the user's experience, but they have too much on their plate right now. This is one of the reasons Unity 8 won't be available by default in Ubuntu 16.04 LTS, even if the desktop is stable and ready to ship. The company is not making the same mistake from 2011, when it pushed a new DE, Unity, to replace the old GNOME 2.x. Shipping a new version of Ubuntu that can't be customized will qualify as a mistake.
