Here's the new Airport board. The world's worst kept secret is that this is actually an 802.11n draft chipset. We're not aware of any way to get the n-functionality in OS X yet, but some have been successful in Boot Camp with drivers for the D-Link DWA-645.

Note the three antenna cables coming into the Airport board. The previous model only had two cables. The additional antenna could provide better reception, or different frequencies (802.11n uses both 2.4 GHz and 5 GHz) for the new wireless chipset.