wow, I didn't know zigbee were planning to go audio....I mean, it makes sense for speech, wireless voip headsets n such, with lower complexity than bluetooth. For CD quality though...unless they add apt-x to it, few codecs would have low enough latency at that quality. Then again....for music, where there is only one source of sound, and non-interactive apps (ie: for listening to music, ipod headsets) it sounds like a winner! Even smaller processors can encode/decode mp3/AAC these days, albeit iwth a total latency approaching 300ms.
For real-time, Bluetooth uses a simplified subband codec, which apparently can run just fine on a small arm7 (perhaps even a dspic, with its MAC hardware). I am still researching that (note: I am out of my depth here).
The only solution I have for 'one-way' audio, is nordics NRF24Z1. No compression, handles all RF and link integrity. Ideal for wireless headsets....my development boards are on their way