Apple has its AirPort Extreme card listed as "out of stock". Is this a sign that an upgrade towards 802.11n is due?
I believe that N uses 3 antennae instead of the 2 used by B and G. Therefore, I think there's more to it than just the card.
There's an upgrade kit that comes with two antennas for the N card. Only the C2D Macbook has 3 antennas. Mac Pro, Macbook Pro, and first gen Macbooks (CD) all have 2.