Marco, I think Columbia's Superbit line is a test marketing of exactly what you're outlining. Will people spend more for a better quality picture but no extras (never mind that the regular version is intentionally downgraded, or that the SB version doesn't actually come anywhere near maxing out...
Much more likely that the industry will ruin HD-DVD by: 1) not agreeing on a format and leaving the technology in smoking ruins in a format war or 2) cropping Academy ratio films to 1.85:1.