For the fourth time, Shuttleworth says that Karmic Koala might receive a new theme, but seeing the constant delays on that one, I am a bit sceptical. The boot process will be overhauled, focussing on improved boot times as well as a flicker-free experience, perhaps by working with Red Hat's Plymouth effort. They are also considering a revamped GDM, providing a better login experience.
A lot of work will also be done on netbooks. Ubuntu will import work from Intel's Moblin project to better support Atom-based netbooks, while also improving the interface to better handle smaller displays. They will also make sure the Netbook Remix is easy to install.
On the server side of things, the focus is cloud computing. It will support the open source Amazon EC2 APIs, allowing users to set up their own cloud using nothing but open tools. The server edition will also better support server suspend and resume, allowing servers to conserve more energy when they aren't put to work as hard as normal.
Ubuntu 9.10 is, as the name implies, expected in October 2009.