There's still the problem that most ODF uploads would be much more suitable as wiki pages. That makes them a lot easier to edit.
Or maybe: it would be nice to have a MediaWiki extension that made collaboratively editing slide sets as simple as collaboratively editing wiki pages.
This would be awesome, especially if they were exportable as slides using the Collections extension.
However, the most popular method of developing slides by far, is by Powerpoint/Keynote/OO.org Impress etc. I don't think there has been developed any good method for converting these kinds of slide sets to the S5 format or a similar format. So while it may be true that "they should just be wiki pages", in reality that doesn't really work. In the absence of good format conversion methods, it makes more sense to aim for collaborative editing of the existing popular style of creating slides.
And in the absence of THAT, it would be nice if we could at least upload ODFs so we can download them and edit them manually (a la SVGs). Being stuck with PDFs only is the worst of all situations.
Maybe this will be less of an issue once the Open Office PDF import extension is more complete?
http://extensions.services.openoffice.org/project/pdfimport
V/r,
Ryan Lane