I don't know how well it works, but I've seen on most of the new displays with the HDMI inputs there is a digital output of some description on the back. For example, I lifted this from the pdf of Sony's 40" BRAVIA™ XBR® LCD Flat Panel HDTV KDL-V40XBR1 display.

You can use the TV’s OPTICAL OUT jack to connect a digital audio device that is PCM/Dolby digital compatible, such as an audio amplifier.

Use an optical cable to connect the TV’s OPTICAL OUT jack to the device’s OPTICAL IN jack.

It also has this discalimer.

The OPTICAL OUT jack is available only when a digital TV channel is received.

It specifically says TV channel so maybe this isn't applicable to another input source, such as a next gen player. Although, it's my understanding that the 5.1/7.1 outputs on the next gen players are because nobody has software yet that knows how to decode the new audio formats. But I think that the media is still supposed to carry a standard DD track. Hopefully someone around here has a little more knowledge on the subject.