Like current SACD\DVD-A players, digital audio through optical or coax digital will probably not be possible. I suspect that audio from BR\HD-DVD players will initially be either FireWire or multi-channel analog outs, with HDMI support following. Just a guess. Then again, its really more the video that they are trying to protect, so who knows, maybe they will allow unprotected digital out.
Any receiver with a Firewire and\or multichannel analog input should be fine.