Japan\'s Sony and Panasonic say they\'re working on a successor to Blu-ray, hoping to offer optical discs holding at least 300 gigabytes of data by 2015. Current Blu-ray discs hold about 50 gigabytes of data. The need for higher storage capability is being driven in part by 4K ultra-high-definition movies -- which offer four times the resolution of 1080p video -- which are likely to come in at about 100 gigabytes on an optical disk. While Sony recently launched a device to stream 4K films over the Internet, it will be impractical for people with slow Internet access or data-use limits on their accounts, making a higher-capacity disc technology attractive. Even with competition from streaming video services from providers such as Netflix and Amazon eating into disc-based television show and movie sales, there will still be consumers looking for disc-based storage solutions, analysts said. \"For the foreseeable future, even with more advances in streaming, there will be a niche for discs,\" Russ Crupnick, a media analyst at consultants NPD, told the BBC. \"But how large that is going to be is hard to say because it is going to be more about the collector and less about everyday usage.\" While special triple-layer 100 gigabyte Blu-ray discs already exist and quad-level 128 gigabyte versions have been promised, neither can be read by a normal player.