Pioneer's 400GB Blu-Ray Disc:

According to the article, Pioneer has improved on the existing BD layer technology to allow for 16 layers of 25GB storage capacity, bringing the disc to a whopping 400GB! And what may be even more impressive, it should be completely compatible with existing BD players. They say to expect read-only discs sooner than later, writable ones in a couple of years (2010-2012), and we should all have our terabyte hats on sometime around 2013.

Digitimes article

Engadget reference