Canonical had earlier released Ubuntu with two different Unity shells, a normal default Unity 3D as well as Unity 2D for old low spec computers without 3D acceleration. But from Ubuntu 12.10, the 2d shell will no longer be available.
Thanks to llvmpipe, users with low spec computers will still be able to enjoy 3D accelerated Unity shell. This will make it easy for developers as maintaining two different shells is a tough work. Unifying the two shells will make it easier to track and squash bugs and also provide enhancements to all set of users.
Ubuntu 12.10 is set to release this October.