The problem is that the existing HTML5 <audio> features are 100% useless for game sound effects and music. There is no specification for playing multiple sounds at once - the latency between telling the sound to play and it actually happening is awful - there is no stereo (let alone spatialised 3D) control - no good way to do frequency shifting - not even a way to pre-load an entire sound file so it's ready to play instantly. None of the existing implementation allow a sound to be looped seamlessly.
Basically, the only thing <audio> is good for is playing background music (and even then...it's not so great).
What the world needs is for a standard like OpenSL-ES or OpenAL or something like that to be added into our browsers - without plugins - and with the kinds of level of cooperation between Apple, Google, Mozilla and Opera that we've seen happening with WebGL.
It would be a match made in heaven.