Also, I think there is only a marginal improvement from the DVD to the HD-DVD format. It's not like it was for VHS to DVD. The DVD format introduced some fundamentally crucial features over VHS:

VHS to DVD

• it was digital so there was no loss in signal quality over time
  
• navigational improvements; you can skip, use the menu to browse (no need to rewind!)
• the DVD is more compact than a VHS tape
• significant increase in video quality
• support for mult-language, subtitles, widescreen, etc.
• extra features like deleted scenes, commentary, alternate endings, etc.
• can be mailed in a small envelope (see Netflix)
• can be backed up digitally

DVD to HD-DVD (or Blue Ray or whatever)

• increase from 480p to 1080i HDTV format (tough too tell the difference)
  
• more expensive

I think that all the significant improvements were covered in the VHS to DVD format upgrade and the benefits of HD-DVD are not significant enough to matter to the consumer.

I would put my money on high-quality streaming video services for the format of the future.