Once they have pumped the buying public with enough incentive to adopt HD as the new mainstream, i would imagine the release of DVD titles will be promptly suffocated very shorlty after.
I bet we're going to get plenty of sub-par HD transfers once HD is the standard, by then DVD will be lost forever.
We vote with our wallets, and many people are already jumping on the HD bandwagon. Yet ultimately, the choice may already be made for us anyhow.