With all that is going on, you throw UDTV into this?
Really, even if, and that is even if, 50% of the US households had HDTV's, that don't mean 100% of them even know what HDTV is. Majority, likely would be happy with OTA digital broadcast (heck, even analong), however, wouldn't be willing to pay more money so they can get HD channels, it wouldn't be worth it to them.
Lets say, 150,000,000 total households (rough guess, considering there is 300,000,000 people in the U.S.), half of which is 75,000,000. And lets say only 50% of those are actually willing to pay a premium for HD, that's 37,500,000 households. Out of them, how many are willing to throw their DVD players away, and run out and buy one of the two HD DVD players? Estimate of 50% would equal 18,750,000. We've went from 150,000,000 to a little under 19 mil already. Divide that number by two, and you've got about 9.5 mil possible for each format. Now, you've got to take off some of those because they are scared away because they don't want to buy the one that fails, and/or can't afford to go out and spend that kind of money right now/are patient for something better to come, etc...
Now, from the other side of the coin, why would any movie companies release tons of HD movies for either format? Especially, when some movies sell more movies than there are possible buyers of HD-DVD and Blu-Ray combined?
This is how I see it.