I'm not the OP, but... The updater's notes specifically mention the 5GHz channel; so no. As far as I can tell, there is no option (at least if you're running WPA2) to select a 5GHz channel using Airport Admin.
We're running a Airport Extreme 802.11n only, 5GHz, WPA2 network at home. My Macbook Pro doesn't seem to have the dropout issue, but both my wife's Macbook and my daughter's Macbook Pro (both are newer than my laptop) get these random periods where their wifi transfer rate basically drops to zero, even with a good signal. Turning the computer's Airport off, and then turning it back on, fixes it.