Here's my little analysis:
the display connector label (vertical line, rounded square, vertical line) is clearly visible, so this port is therre to connect an external display device. It's the shape of the mini DVI but smaller. The Macbook Air's micro DVI looks more like a standard USB connector. So why didn't they use the normal micro DVI? Maybe this thing is a dual link port so it can drive 30" displays.
EDIT: sorry for the "realease" typo.
My reasoning exactly. They can't just insult people who need a dual link by not including this functionality. I'm 99% sure that it's just a new connector that has dual link support.