Last week, Bill Filler from Canonical created a flutter when he announced Unity 2D for computers which cannot run the normal Unity 3D. Unity 3D requires Compiz and thus requires computers capable of 3D-acceleration to run. Unity 2D, technically known as Unity-Qt, is based on Qt/QML and has been designed to run on the slower computers.
Earlier the belief was that if a computer is unable to run Unity, it will fall back to the classic panel based GNoME desktop. But Filler's announcement led everyone to believe that Unity 2D will be the fall back option.
In an interview with Linux Pro Magazine, David Barth, Engineering Manager for Desktop Experience (DX) Team, at Canonical, has said that they have no plan, at the moment, of including Unity 2D in Ubuntu 11.04 Natty Narhwal. He said that the classic GNOME desktop will remain as the fall back option in case a computer is unable to run Unity 3D.
It's not on the Natty plan for now, but we'll be evaluating the progresses and will consider adding a 3rd session option if the development goes as planned. For Natty, the plan is still to have Unity 3D and the Gnome classic session as a 2D fallback. The classic Gnome desktop will be kept as the safe and recommended default, even if a 3rd session is added. This is important for a lot of our users, in the community or in enterprises.
So, considering that Natty is nearing its second Alpha and Canonical does not even have any plan to include Unity 2D yet, I think it will not make it to Natty- which is a same really.
However, there is a PPA available for Unity 2D and any user can install it easily.
(Careful, the PPA contains experimental packages.)
sudo add-apt-repository ppa:unity-2d-team/unity-2d-daily
sudo apt-get update
sudo apt-get install nity-qt-default-settings