The new iPhone should be this:

Both the keyboard and screen combined for $300 or $300 each?

Proably $300-500 for it all

Does that mean the total cost of it will be $300 - $500 more than the iPhone 4s?

Too many buttons.

I think they could sell the dock between $300-$500 although I think it is better suited closer to $300. I know plenty of people that still prefer a computer interface to that of an iPad(or really any tablet for that matter) that would be inclined to purchase something like this, so they can use the features without giving up the interface they like.

As for the NFC idea, I like it in theory, but I still would rather have my docking design for a couple of reasons:
First, I like my design as being "seamless", fitting nicely as though it belongs, not as though it's just set on top
Second, I like the idea of my phone being secure in this design. A mobile device should be mobile, and I think you put one of your devices at risk when you are trying to juggle the two of them.
Again good in theory, not so much practice.

Edit:
After rethinking this, I have no idea what they could sell it for. Realistically, during docking, it would be using an iPad version of an app so the resolution would have to be as high as the new iPad, so after taking that into consideration I fear the price of a dock would be closer to $500. It can't cost more because the iPad starts at $500(for the new Retina Display) so removing the "guts" and leaving the display and battery + adding a keyboard can't put it over $500

That thing is undeniably ugly.

This is pretty cool.

Really?

Yes