Can't remember the companies name right now, but a company developed a coating for BR Discs that make it more impervious to scratching than even current gen DVD's.
Ah! But the difference is that High-Def can be slowly phased in on a hardware level until it reaches critical mass without Joe Sixpack even knowing. If Players convert to hybrids-only, in 5-10 years all players will be High-Def capable. Unlike Laserdisc where it wasn't able to play any...