The Blu-Ray Disc Association has now made it official that the official specs for Blu-Ray discs will be backwards compatible. The PS3 game consoles will be able to play 3D Blu-ray discs as well as expected Blu-Ray disc players. They will be using Multiview Video Coding (MVC) and will make use of 50% less space compared to the usual 2D content. They will feature full 1080p as well which should ensure HD quality viewing as demanded by consumers.
(Source) Slippery Brick