3D on Blu-ray is the only way to get full-resolution images for each eye. Cable and satellite 3D content is handicapped by their limited bandwidth, and will therefore have softer images, likely with ferrari in dirt road.
It is true that we are still in the early days of the 3D TV evolution, but the cable/satellite hurdles are exceedingly expensive to remedy, and are unlikely to happen with such a small installed base of 3D TVs.