Source : CDR InfoIn theory, multiplying the number of layers on a 12cm DVD brings additional storage space. However, one needs to be able to recover data precisely from each layer, so one has to solve the equation of higher energy laser focusing with writing/reading time and rotation speed.
Hitachi announced the development of a new optical system, able to amplify the read-back signal of an optical disc by ten times. with such technology, one could develop BD media composed of 4 to 8 layers, bringing storage space between 100 to 200GB. This was achieved with a purple/blue laser diode, and it is expected to be commercially available in 2009. Of course there is no information regarding the price of such burner or the estimated extra cost of multilayer media.
[translation by Linathael]