The Mission Repair blog has posted photos of what looks to be the back case of the next-gen iPad. The new case sports a second dock port hole, which could be for either docking in landscape mode or a SD card slot.
Mission Repair has had a shaky history with calling Apple equipment. They got their hands on the 1st gen iPad shell where they, correctly, posted the internal antenna but incorrectly talked about the space for the camera (it turned out to be an ambient sensor)
Apple already includes SD card slots on the Mac Mini, iMac and MacBook Pros – so it makes more sense that it would be an SD card slot rather than a landscape dock port.