As more and more people go for fixed pixel displays (many that have terrible scalers to native res) the HD formats will do well to show off the best PQ of the respective panel compared to SD DVDs that must be scaled to native.
That being said, shiny discs are likely to become a niche sooner rather than later - the advantages of portability aside, the studios would no doubt -love- to tie all content reproduction to a specific IP-style address, controlling distribution through the life of the film. In a future with blanket ultra highspeed and unlimited bandwidth (heck, there's wifi on planes now) it seems that the physical medium for films will be totally beside the point.
I frankly wouldn't be surprised if the death of disc shows up within a couple years, with tentative launches from the studios already taking place within months.
With terrible resolution to begin with (I believe apple is doing 640x480 for their recent launch), HD discs will be far better in the short term. However, if on-demand blanket HD is available at a reasonable 1420x1080 (or whatever the res is for satelite HD), compressed with a new and optimized algorithm, the need for shiny discs will be for those who a) have a old skool love for media in their hands, b) very high-end setups where they can tell the difference.
A vast, vast majority can't tell Mp3 from CD on even the most capable of systems, let alone the jump to high res. When most listen to MP3, they don't feel they're missing anything - sure, a/b'ing shows them the sonic elements that are being discarded, but the quality is better than the radio most of us grew up with. The same may happen to film, "good enough" pic with the convenience of instant access to all films from all libraries with a single account broadcasting to our hand helds, our TVs, heck, why not straight to the back of the retina!
Do I think the ubiquitous strawman Joe6p will get gaga over HD discs at home? No, I don't. I hoped for DVD-A to become more mainstream (DualDisc looked like it might help), and thought that Sony just might make SACD hybrids catch on with cheap replication costs (added content of 5.1 makes you want to purchase the disc rather than just torrent the hell of the songs).
There's an entire generation growing up without any connection to music served on in a physical way, let alone paying for that music. The same can be said for films and TV shows. I personally missed home celuloid presentations, but I came way after those of you on this board that may have had their first home theatre showing 8mm prints with 20 minute excerpts of the flick, or those like Robert Harris, et. al. that own 16mm and 35mm prints for showing at home. For me, the connection to celuloid is now strictly a niche that is likely to be abandoned in the next decade with a move to digital, save for certain special venues like Imax. Similarly, I doubt HD discs will last as long as DVD has, let alone VHS or LD during their run.
Conclusion? Get them while you can, enjoy the hell of the flicks, love that some of your favs are in the best format you're likely to see for some time. I know that's what I've done with my DVD-A/SACDs, some must-have titles that make owning players for this media a must for my system. I will own a player to play Lawrence of Arabia and another to watch Kong, just as I own an audio player for Dark Side of the Moon and early Elton John, and another for Pet Sounds, Harvest, the Polyphonic Spree and Rumours.