The Blu-ray Disc Association is working on a set of specifications for building 3D-enabled Blu-ray players. The plans include two streams of 1080p video, one for each eye (as we've seen from Sony and Panasonic's systems).
The Blu-ray Disc Association is also looking to ensure that 3D players will play 2D content and allow you to watch 3D discs in 2D if you need to. But it will be possible for content providers to require 3D only playback.
Guidelines and specifications will be published in December 2009 so 3D Blu-ray players should be with us in the first half of 2010.