Generally, I agree with your point the DVDs are here for a while, just like the CD format has stayed just about constant for almost 20 years. On the otherhand you say:
HD-DVD and BluRay are competing for the niche markets formerly occupied by products like Laserdisc. Their proponents may *think* they're aiming to replace DVD, but that's a lot more enthusiastic than realistic.
DVDs were adopted very rapidly compared to the average electronic consumer device despite the existance of tape. HD formats might follow a similar pattern.
While there aren't many adoptors of HD-DVD or BluRay right now, the emerging prevalence of HDTV monitors makes it a likely that the uptake will be rather fast going forward.
I don't have a HD set yet, I've been waiting for more content, a reasonable HD tivo device, and a HD DVD like device. When I make the upgrade to my TV display I'll likely want to buy my movies in the new format to take advantage of the investment in the HD set.
Nothing is too wonderful to be true
-- Michael Faraday