Having a quick look around the industry news for the past week or so, we found a little gem:

TDK has announced at the CEATEC tech event in Japan a new BD-R disc with 320 Gb capacity. This has been achieved by creating a ten layer version and adjusting the light transmission properties of all layers.

Presently, the specification allows for a maximum of eight layers only. However, as TDK is a member of the Blu-Ray association, they have mentioned that they intend to propose an extension to the current standards to accommodate this and also the adjusted track pitch which is required. 

From a manufacturing perspective, this is a very complex recordable media. The potential for losses or poor yield from the manufacturing process are massive. The technical complexity and stability of the manufacturing platform would cause it to be orders of magnitude more expensive than other current recordable media disc products.

In other words, it won't work on current hardware and you would need new hardware which would be at a significantly higher cost, let alone the cost per unit of the recordable media. 

Red Circle's recommendation? If you need a 320 Gb transportable storage medium, use a hard disk or mag tape for now. 

And remember: never underestimate the bandwidth of a speeding motorcycle courier.