It's worth mentioning that Sony and other companies have made a Blu-ray disc capable of holding up to 100GB:
http://www.amazon.com/Consumer-Electron ... -ray+100gbApparently, they can hold up to 4K and play on normal Blu-ray players just fine. The Tsuburaya Blu-ray sets such as Ultra Q and Ultraman, despite having 3 episodes per disc, using are this 100 GB disc.