"5G" is confusing marketing language from Broadcom.
This has nothing to do with cellular (3G, 4G). It is the thing beyond .11n. Atheros and all the other Wi-Fi chip makers are likely to pitch it as the successor to .11n.
But the truth is the Wi-Fi roadmap is splitting into fast 5 GHz, ultra fast (but short range) 60 GHz and ultra long range 700 MHz (if regulators make spectrum available). But that's a harder message to communicate honestly.
Meanwhile "5G" just sounds cooler to the marketing department at the risk of confusing consumers.
Well, a and b both came out at the same time in 1999, so in a sense, they are both 1st Gen.
And 5G couldn't really mean 5 GHZ, since that is nothing new -- even the old 802.11a operated at 5 GHz.
Either way, if I were the Marketing guy at Broadcom, I'd call it 5G for the simple reason that consumers will understand it to mean "better than 4G"...and don't worry about the fact that here we're talking about a WiFi standard, and the whole 3G/4G thing is a cell phone standard.
I am sure he meant both 5G and 5GHz. Put on your Marketing hat for a minute and looks at the blistering data rates on 802.11ac. Now think like a consumer, whose eyes roll over when you start talking megabits per second.
But consumers have an intuitive understanding of the "G" nomenclature used by wireless carriers -- prior to 3G meant painfully slow, 3G is sort of decent speed, and 4G means wow, it's finally become true broadband. But 5G? Wow, 5G must be insanely fast! And in fact, it is.