It looks like iChat will also be getting an upgrade in Leopard. The application looks like it will be expanded with advanced whiteboard features.
On April 24, the European Patent Office revealed Apple patent DE69634950T titled "Method and apparatus for establishing communication between two teleconferencing endpoints," in which Apple details many of the new features that will be available. While patent information shows that Apple has been working on this since 1995, the emergence of this new European patent suggests that it is now ready for prime time and will be surfacing.
iChat AV 4 will enable users to share a common active window, which will allow for 2 way interaction. This digital 'whiteboard' can contain different types of media from images, sounds and movies to text documents, spreadsheets and other graphical data. This data is shared by all participants in the teleconference and can be manipulated by all of them.
While these new capabilities will be interesting, the fact that iChat is not very widespread cuts down on their impact. If Apple were to make the program compatible with more instant messaging protocols, or release it as a free program for Windows, like it did with iTunes, it would go a long way to seeing more people use the program.