The Canon 5DS is now shipping in large quantity and remains in stock for the time being. If you pre-ordered the camera, it should be on its way to you. And, if you still want to pick one up, it looks like there is enough stock to go around. Check it out here at B&H Photo.
The Canon 5DS R should be shipping soon but is, as yet, not listed in stock. Check it out here at B&H Photo.