That's only a couple of years old.
Wireless tech available to the general public has not changed significantly during that time.
There are several of the wireless tech companies that are currently releasing tri- and quad-network routers, with higher performance CPUs, etc. I don't know if Apple would go for features, unless they end up with stability, too.
That being said, there may be some announcement soon, if an updated AppleTV is released, about updated Airport Extreme to match up with that. We all may know more in just a few days, eh?