http://blogs.msdn.com/b/ie/archive/2011/03/16/html5-video-update-webm-for-i…
It appears to be a little rough around the edges, but should bode well
for Wikimedia video support as IE 9 starts to be pushed out to windows
machines and ideally we won't have ie7 and 8 for as long as we have had
IE6 ;)
If you have not already seen it, the TimedMediaHandler extension
supports transcoding to both webm and ogg for mediawiki video assets:
http://prototype.wikimedia.org/timedmedia/Main_Page
I will integrate links to
http://tools.google.com/dlpage/webmmf/ for IE9
users in the mwEmbed player once the components are working a bit more
smoothly.
peace,
--michael