Blu-ray, at its largest (BDXL), would be able to store anywhere between 100/128GB and while that might be pretty sizeable for the average user, it seems that professionals might not think that is enough. For professionals working in the music or film industry, burning through gigabytes worth of data is not an issue, which is why Sony and Panasonic have recently teamed up to offer a new storage medium called Archival Disc.
As the name implies, this method of storage will be used to archive data. Unlike BDXL, Archival Disc will be able to store as much as 300GB, and in the future there are plans to offer up 1TB storage as well.
The format will primarily target professionals who might require such huge amounts of storage on a disc-like medium, but perhaps somewhere down the line when the technology becomes cheaper and more ubiquitous, it could see mainstream adoption as well.