Although there was an announcement almost 2 years ago regarding VP8 support for Flash, there was no commitment made to support the Matroska container or Vorbis

Although there was an announcement almost 2 years ago regarding VP8 support for Flash, there was no commitment made to support the Matroska container or Vorbis codec at that time, which are both part of the WebM spec. Since then there has been no release or further communication on the topic, afaik. Looking around the web a couple months ago I found an experimental implementation of WebM decoding in Flash by Ralph Hauwert, but my understanding was that it was only able to achive 5-10 fps due to high CPU usage and no built in hardware support.