And, when they say High Definition, what format are they talking about? 780p, 1080i?
I'm not sure that's been finalized yet. The HD spec wars have been all about the physical format so far -- Blu-ray vs HD-DVD. Looks like HD-DVD is going to win (which is probably good -- particularly for computers; there's a lot higher data density available on HD-DVD IIRC).
If they were consumer friendly they'd make it 1080p and have either the player or display downrez as appropriate.
If they're company friendly then it'll allow either 720p or 1080i. That leaves a nice upgrade path to 1080p or higher in the next decade.
FWIW, the best film->digital conversion process uses 4096 lines of resolution. That's pretty well accepted as the absolute limit for film resolution, and is well beyond the resolution available for a lot of film. So if you want to think pie-in-the-sky, then ask for a media that can do 4096p. Then you'll be good until we go holographic/3D. It won't be HD-DVD or Bluray though; they don't have the bandwidth or the storage capacity. It'd probably take an ultraviolet laser for that kind of density. That or holographic storage media.