Unfortunately I can't tell you much about ARM processors. But I will remind you that radios are getting more efficient - just look at some of the "n" AP's that are running POE successfully with only one Ethernet connection. Now that's an improvement.
Also,due to the increased sensitivity (in dBm) of receiving radios, less power is needed on the transmitting ends of a link.
However, he does have a point and "n" radios especially will be using even more power.
Which brings up a question - has anyone done comparisons on the various "n" MCS indices, on any "n" chip set, and how efficient they are when compared by throughput versus power drain?