Dual-layer Blu-ray discs are so 2006. The new hotness is Pioneer's just-developed, 16-layer Blu-ray disc (pictured above) with a whopping 400GB of writable storage space. For reference, that disc could hold roughly eight copies of Metal Gear Solid 4, 187 copies of Final Fantasy VII, or 1.25 million copies of the original Super Mario Bros.
The new discs require a special "wide-range spherical aberration compensator and light-receiving element" to detect the weaker laser signal, so don't plan on sticking one of these data-bloated monstrosities into your existing PS3. That said, the next generation of game consoles could support this new disc system, which is fully backward-compatible with existing Blu-ray discs. Of course, by the next generation, game systems might not be using optical discs at all, so who knows what the future will hold.
