Take that HD-DVD ;)
"About a month ago, Pioneer announced that they had developed a 400GB Blu-ray Disc. Not satisfied that they had exhausted all avenues, they continued developed and found a way to add four additional layers, bringing the total disc capacity to 500GB. As with the 400GB version, the disc is compatible with current Blu-ray drives found in computers, players, and recorders."
http://www.blu-ray.com/news/?id=1616