Well, DVD's at 720, not 480, so even standard DVDs look better on your HD TV than a regular TV.
Look at it this way: DVD's been around for over a decade, and there are still essential films that are only now being released in that format. How long until there's an HD Stranger Than Paradise?
When HD is readily available, the next format will be on the horizon. Will you not buy any HD DVDs in anticipation of Super HD?