Hi justforkicks,
The problem with creating presentations from XML is that many people refuse to use something that is not a WYSIWYG editor, and OpenGoo aims to be usable for everyone. Maybe it would be cool to have both alternatives, like with FCK (where you can write HTML with the WYSIWYG editor or by editing the source code).
With our presentations (Slimey) editor you can edit the source to some extent, which is XHTML with CSS, but I know it's not very practical. The problem with Slimey is that it hasn't evolved since its first release, because we prioritized many other OpenGoo features which are usually more important to users than creating presentations. We would gladly change Slimey for a more mature Open Source presentation editor, but it should have a WYSIWYG interface.
Concerning moving towards video presentations, I agree that slides are getting old, but people still use them. I guess slides are the right tool for some cases. I personally don't use slides too often.
I'll have a look at those video editors that you posted and see how they could be added to OpenGoo.
Thanks for your info and ideas!