During one of his presentations, Blaise Aguera y Arcas eluded to some work in the pipe on generating higher density point clouds from synths.
From the way he described it, the synth process uses an algorithm to find matching features between images that don't depend on a particular geometry of the camera, orientation, etc. The resulting point cloud is relatively sparse, but contains enough information to tie the images in a synth into a cohesive geometry.
Once that geometry is known, however, from what he said it should be possible to take stereo pairs and apply a different algorithm to pick up common points in the pair, and tie those back into the geometry as well. From the example he used in his talk, this algorithm creates a much MUCH higher density point cloud.