The video and audio tags of the HTML5 specification are important to the future of the web. Video on the web used to be provided through things like QuickTime and RealPlayer, technologies which were later replaced by embedding video inside Flash. Both of these solutions are not particularly ideal, as Kroc already explained.
Firefox, Opera, Chrome, and Safari all support the audio and video tags, either using the operating system's media framework (Apple) or through built-in codecs (everybody else). Microsoft, still the largest browser vendor, had so far not said a word about these tags, hindering adoption.
This has now changed. Microsoft's Internet Explorer Program Manager Adrian Bateman kick-started a thorough discussion on the HTML5 specification early August, detailing a number of issues it saw with the then-current draft. "Adrian Bateman did what no man or woman had ever done before: he gave substantive feedback on the current editor's draft of HTML5 on behalf of Microsoft," Google's Mark Pilgrim writes, "His feedback was detailed and well-reasoned, and it spawned much discussion."
It took a while, but a month later, early September, Bateman more or less officially endorsed the audio and video tags, which could mean that we might see them in whatever next version of Internet Explorer. Bateman stated it rather drily: "We support the inclusion of the video and audio elements in the spec." Microsoft does have a two concerns, though.
First, the company believes the tags should allow the streams to notify the page of certain events, so that for instance a transcript can synchronise with playback. Secondly, Microsoft proposes to include additional information within the source elements of the tags (more on that here).
Technically, this endorsement does not have to say anything about the future prospects of the tags in Microsoft products, let alone the method Microsoft will choose. Most likely, the company will opt to go the Apple way, and use the DirectShow/Media Foundation frameworks.