I can't claim to be the ultimate expert on this subject, but from what I have seen, the problem appears to simply be that we don't know. There will be audio via HDMI for any HD format. There will also be new audio formats (Dolby Digital Plus, for example). The catch currently is that nothing beyond that is quite finalized - if you look at the Blu-Ray FAQ, for example, the supported audio codecs are not even worked out yet. Will DD Plus and its DTS counterpart require the bandwdith of HDMI? It's a possibility, although some of the literature I found on DD Plus suggests that it is intended to work within existing bandwidth limitations and even to allow compatibility with existing DD decoders (presumably without the full benefits of the format). I would assume that there will still be audio data of some sort available via optical or coaxial digital output, but since things still seem up in the air with both HD disc formats it's hard to tell for sure what that data might include. Heck, there may even be non-technical reasons (copy protection, specifically) that lead to any new audio formats being restricted to encrypted HDMI or multichannel analog output from HD disc players, similar to the restrictions placed on DVD-Audio and SACD. Time will tell...