So I guess you are forgetting that Apple also
ships a VGA Adapter? All you are doing is stepping on your own toes with your statements.
I don't see how docking has anything to do with this considering the VGA adapter Apple sells doesn't even allow you to dock with anything since it's already taken. It's just impossible. It wouldn't need to be upright anyway as you are going to be looking at whatever display you are hooked up to. You could lay your iPad down and have one standard dock connector charging cable coming out of the bottom and a mini-display port going out of the top. Whether it happens or not is irrelevant because I said possibly. Your argument that an SD Card slot could be possible but a MDP couldn't doesn't hold up.
I didn't forget the VGA adapter, but I purposely didn't mention it because the dock port is a universal video out port. It can be purposed for any type of video output that Apple chooses and that is why they sell many different adapters for it. Doesn't matter if it is VGA, Component, Composite, or (potentially) HDMI or MDP. I knew you would bring this up though, and I just couldn't leave our wonderful conversation unfinished.
Also yes you can use the VGA adapter with the dock, you simply plug the adapter into the back of the dock. The dock connector is designed to be the only A/V hook up on Apple's devices, other than the headphone jack. They aren't going to change years of design to put a really odd MDP port on the top. Plus what happens when you plug in video out on the dock connector and the MDP port at the same time? What is the point in that?
Sure anything is "possible" but the probability is incredibly low.
The fact is that the SD card slot is more probable because of the demand for the camera connection kits. Apple sold out of those for weeks at a time, while the VGA adapters all got returned (and barely bought at all) once people realized how useless it was. We also have had rumors of an SD card slot for months now, and this MDP rumor only just came up by some random guesses from people writing about the leaked cases. They guessed wrong though, it's quite obvious.
Besides, everyone keeps ignoring the fact that none of these leaked cases have a hole cut out for the microphone, which means the hole at the top is the most likely place for a new improved microphone.
So in terms of the chances of the things happening, they go in this order:
FaceTime w/ Front Facing Camera
Rear Facing Camera
Faster processor
More memory
Better Speaker & Microphone
SD Card Slot
...then way at the bottom of the list of chances...
Mini-Display Port (a second video output port besides the dock connector)
Retina Display