How about a disc that is made of glass, has a capacity of a DVD and can be read by standard dvd players and can be bought today, for a mere of €160? THIS is amazing. http://www.syylex.com/index.php/home_english.html
The reflective layer is still made of metal and the two layers are glued together. You have to take the maker's words on how durable those actually are.
Well, sure - but even if the reflective layer loosens, you still have the glass layer - then it would be the same as the hitachi concept: read the glass pits with a miroscope. Or add a new reflective layer.