It's most likely not one of the 11 pins missing. On the current 30 pin version: 8 pins are used for firewire, 2 are used for composite video out which has only been used by the ipod photo, and 1 is used for s-video luminance which has also only been used by the ipod photo. There are the most likely 11 that will be removed.
Removing basic audio output would be just silly...
Ok, that destroy my guessing with a good argument; hard to beat.
Keeps me left with the mechanical stability only