I thought the devices already did this since they tend to drop the CPU clock from like 1GHz, to 50MHz when the device is on standby so it would make sense to downclock the wifi radio and reduce it's polling rate to a bare minimum level.
(PS for windows mobile there was another way of reducing the wifi power issue( You put the wifi radio on a schedule, it runs on for a very short time every few minutes (or how long you want the delay) and it checks if theres any new info for it to get)
The benefit is the wifi may only be enabled for like 30 seconds per hour, allowing you to save power.
if they can do that with new wifi hardware and combine the scheduling with the reduced clock rate, then you will get much better battery life out of your devices.
I currently have a hp touchpad and the wifi power management sucks. when in standby, your only option is wifi off or on, when it is on, it is connected to the access point 100% of the time at full rate, (while the standby time is still extremely good, it is better with wifi off, (cant they strike a balance between these 2 extremes?)