Nobody uses VP8, but Google is already working on its successor
The VP8 codec hasn't made the splash Google and many others had hoped it would, but Google is already well on its way to building its successor, VP9. In fact, recent Chrome builds now come with experimental VP9 support.VP9 is the next-generation video codec and a relatively recent addition, so much so that there are little details known outside of the core developer circles.
While Chrome 25 in the dev channel supports VP9 decoding, it's still very early in the process and the feature won't be of much use to anyone but devs working on the codec. Still, the latest libvpx library supports VP9 and that's used in Chrome.
Also new is support for Opus, the brand new audio codec, spearheaded by Mozilla. Technically, it means Chrome supports WebM files which rely on Opus for the audio, though you'll have a hard time finding these. The feature is also disabled by default and hidden behind a flag.