It's ultrafast femtosecond pulse lasers, spatial light modulators, and lab-quality fused silica glass. Nobody has ever put any of those into a consumer product before. The CD combined microscopic feature casting in plastic (same technology used for phonograph records since at least the 1930s if not the 1890s), metal-plating of plastic (from the 1950s), room-temperature semiconductor lasers (from the 1970s, although I don't know when their first mass-market product was), error-correction codes (commonly used since the 1940s), and PCM (from the 1930s, but, I think, only then being rolled out on a grand scale for digital telephony). The only one of the component technologies that might have had uncertainty as to its suitability for mass-market uses would have been the semiconductor laser diode, and in theory it wasn't necessary — you could have built CD players with HeNe lasers like the ones being rolled out in supermarket barcode scanners at the time, and which had been used for freight-car barcode scanners for a decade, but they would have been heavy and fragile like a tube radio or fluorescent light, not rugged and lightweight.
Aside from this, the storage technology itself might turn out not to work. It's holographic, and extrapolating is perilous in holography — some small source of noise that isn't significant when you have a megabyte of data recorded might turn out to be overwhelming when you have ten gigabytes of data recorded, let alone hundreds of terabytes.