In a few years from now.. say roughly 5 years maybe?
When HD-DVD is emerging on PCROM, and games ship with this format - what do they do?
By then, they'll of course still be using DVD as well. Just as it happened with DVD and CD.
After some time, when games use all the space on DVD, they ship with two or three DVDs, or even four.
In this case, the same game will be available on one HD disc.
You really won't be needing a HD drive for a long time.
And by then, it will be as cheap as DVD, if not cheaper.