Mozilla may have ulterior motives. They don't need to implement h.264 support. Just like they don't have to implement mp3 support for you to hear mp3 streams. A plug-in could do that. A plugin written by someone else. But there's no way for anyone to write such plugin that would deal with HTML5 video decoding. If Firefox can allow Flash and various "Media Player" plugins to play H.264 video, why does it not allow another plugin to play H.264 in HTML5 videos?
No announcement yet.
Adobe Rants Over Linux Video Acceleration APIs