If DD is to succeed I think it'll be reguardless of a HD Optical format.
I believe it's success will be more along the lines of downloadable music, not based on absolute quality but being good enough and more convenient.
I still think the primary reason for CD adoption over LP was convenience, the same for DVD over VHS, and I think this is why formats like SACD/DVD Audio floundered, and why Hidef optical disc formats will continue to flounder. For most people they are simply no better than the previous generation.
I have 50+ laserdiscs and a massive DVD collection almost all of which was bought at full price, and I own 0 Hidef discs, partly because of the format war, but mostly because I'm sick of storing the disc packaging. I'll take a lower quality copy of something I can find and watch quickly over something I have to find on my shelves.
Now I'm clearly I'm atypical, but I really believe that a new format has to offer something above and beyond improved picture/sound quality to be successful in the mass market.
Think that DD is a ways off and not because of bandwidth, the thing that will hold back DD adoption will be DRM, I just had to explain to my GF why she could only stream some of her iTunes songs to one of the media players on my network, and to her it was just broken. And I happen to agree.