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.

Also, it occurs to me that megapixel spatial light modulators are also the key element in megapixel projector displays, so that might also be already ready for prime time.

Fused silica is already mass market. It makes up the bulb in halogen lamps.

I know, but I don't think it's particularly high-purity fused silica. I admit I'm guessing, though.