I believe it will be absolutely essential for the next generation Airport Extreme (Sixth) to be out in 2013 especially prior to the March 2013 release of the new, new iPad 4. The New iPad 3 has been criticized for poorer WiFi reception as compared with the iPad 2 partially due to its larger battery partially blocking the WiFi. So Apple will absolutely need this by March 2013.
However, I can see the Sixth Generation Airport Extreme coming out now, however. Netgear came out with a Gigabyte WiFi unit R6300 and so did Buffalo. So Gigabyte routers are here already even though there are no devices out as of yet.
I believe we will see the next iMac next month come equipped with Gigabyte WiFi 802.11AC already.
In October 2012, the iPhone 5 will have the Fifth Generation Gigabyte WiFi 802.11AC on it I feel.
From what I have been reading, Apple has a history of using generations of WiFi years prior to their official ratification by the IEEE. So far, no equipment has been rendered useless because of this. It will be a relatively simple software or possibly firmware update to maintain the WiFi current when the standard is finally ratified. I just wonder what is taking the IEEE so long to ratify the standard? And why the IEEE has a history of waiting too long. After all, Apple had the Fifth Generation Airport Extreme out years prior to the IEEE finally ratifying the current Fifth Generation 802.11N!
Dr. Saponaro