The Blu-ray Disc Association recently announced the competed specifications for Ultra HD recordable media. It's intended for use in Japan, where physical media sales of Blu-ray discs are still very popular (as opposed to here in Britian, where people might prefer 4K HDR iTunes movies).
In fact, 75 percent of the Blu-ray hardware market in Japan is taken up by dedicated Blu-ray recorders, vastly outstripping standalone players. The new format allows off-air recording of UHD content, with players slated to become available in time for the Tokyo 2020 Olympic games - which, while recordable in 4K, may yet be broadcast in 8K.
A triple-layer recordable BDXL disc can hold up to 100Gb, while a quad-layer version can reach 128Gb of storage. This is more than sufficient for storing HD broadcasts, and should even accomodate 4K and 8K broadcast footage.
Victor Matsuda, Chair of BDA Global Promotions Committee, says he is "anticipating that Ultra HD broadcasting will start in Japan around the end of 2018. The ability to continually expand to keep up with consumer demand for high quality experience, remains one of Blu-ray’s greatest strengths, and a primary reason for its success and longevity.”