I was in Chicago visiting my family for Christmas. I rented an HD movie from the iTunes store and it took over an hour just to buffer it. Turns out my uncle only had 3mb down and 1 up. Paltry! At that rate the movie would have kept buffering.
I really don't think Apple is going to use a brand new connector when they just spent several years creating the Lightning port.
If anything they will likely make the port on the MacBook Air a Lightning port to match the iPad and iPhone.