As we've announced back in May 2012, Canonical planned the removal of the Unity 2D project and make a single, stronger and smarter Unity interface for the upcoming Ubuntu 12.10 (Quantal Quetzal) operating system.
Now it's official! Canonical removed a few days ago the 2D variant (the Qt non-accelerated version) of the Unity interface from the current development version of the Ubuntu 12.10 (Quantal Quetzal) operating system, which will be released on October 18th, 2012.
The reason behind this decision is probably the too much work involved in the main Unity version - maintaining a "clone" requires even more man power - which brings us to the new Preview feature detailed in this article.
For the Ubuntu 12.10 (Quantal Quetzal) release, Canonical will definitely prepare an improved and revamped Unity interface.