it is a feature that attract users to come to ubuntu, since it's pretty and most important, efficient. any hopes it will be available to use in the next unity release 11.10?
Unity is designed to use the Desktop Wall plugin, and I don't see any reason why they would change it. In fact what needs to be changed is the Desktop Cube plugin itself, as it does not support vertical layouts (as the KWin cube does).
Unless someone does the necessary work to add this feature and fix any bugs, it will remain essentially the same as it is in 11.04.