HD DVD's dual-layer 30GB and Blu-ray's dual-layer 50GB media simply won't cut it for movies in the future or at least media manufacturers do not believe they will. Multi-layered discs seem to be the expected road to take for the high definition war. Ritek has claimed to have successfully designed a deca-layer (10 layers) disc that can be applied to both HD DVD and Blu-ray formats. That would equal to 150GB for HD DVD and 250GB for Blu-ray, assuming 15GB and 25GB layers, respectively. Ritek officials, however, remind us that the real limitation comes from the reader and writer laser diode technology, not the physical disc.
Meanwhile, Toshiba Corporation seems satisfied with their developed triple-layer HD DVD-ROM (read only) disc with a capacity of 51 gigabytes (3 x 17GB). Where'd they get that number? Yes, HD DVD discs normally hold 15GB per layer, but an extra 2GB has been squeezed in thanks to improvement in disc mastering technology. So basically, you have the Blu-ray dual-layer or the HD-DVD triple-layer for ~50GB of space. Thanks to the same physical disc structure as a standard DVD, Toshiba has said that three layer discs are not much costlier to produce. Toshiba aims to secure approval of the new disc by the DVD Forum within 2007.
News source: DailyTech