They could probably get a good chunk of improvement out of Theora if they broke the spec, fixed a couple of things that either seemed sensible at the time or were just plain stupid and took advantage of what we've learned about codecs and assumptions about processors speeds and capabilities in the meantime.<p>They haven't done so yet because there's still room for improvements to be wrung out of the current spec and the longer they wait to do a non-backwards compatible spec break the better they'll be able to make it.<p>If Google releases one of the VP codecs then it's probably not going to be that much better than what xiph could have done if they weren't trying to keep compatability since they're based on the same core technology.