Actually, the end of KFOG simply signals the end of AAA as a viable format. It is also on the decline in Portland, mostly due to aging. Same in Chicago with WXRT. It is very much alive in Denver, but that station has a very strong community heritage going back to the late 70's when Bob Greenlee opperated it and had Dennis Constantine as PD.
But elsewhere, AAA is pretty much an aged out non-viable format.
Strange you say this as there seems to be an article every year talking about the vibrancy and importance of the AAA format, whether as a tastemaker for new music or as a way to bring generations from Boomers to Millennials together. Is it wishful thinking or is this like the alternative format in the 80's, having ups and downs before a breakout moment?
WXRT was in a extremely KFOG-ish position a couple of years ago as they were the last defiant holdout when it came to alternative rock on AAA. They preferred to use the 60's/70's soft rock/AOR recurrents from their past as that's what their drying pool of listeners wanted. The new PD that took over after the Entercom merger saw an opening with The Loop gone and WKQX largely turning into a glorified pop station and took it. There is no rock station playing anything after 1990 with WKQX shifting to indie pop and the Loop gone so WXRT was going to play those songs and hope the audience was there. They had nothing left to lose.
WXRT has peaked as high as 1st in Chicago after incorporating artists like The Killers, The White Stripes, Garbage, STP, The Cure, Nirvana, Alice in Chains, Franz Ferdinand, etc. Into their playlist. They also discontinued some specialty programs that had been getting a miniscule but loyal audience for years. WXRT did sacrifice some of their loyal listeners by incorporating 90's/00's alt rock but not all of them, and they're solidly in the top 10 every month.
It helped that they didn't ditch all of their soft/AOR rock that the diehards cling to, and the playlist flows well enough that there's never a jarring transition.
WXRT has also been smart with song selection from the artists they added. You're not going to hear "Rooster" or "Again" by AIC, but "No Excuses", "Down in a Hole", and "Don't Follow", as an example. They did an appropriate amount of listening and research to figure out what songs would mesh well with their heritage.
Also, KFOG had switched from AAA to pure alternative, so if anything this reveals that San Francisco doesn't have room for more than one alternative-formatted station. In a city where two news stations are far and away the most popular stations the music stations are competing for scraps and you can't have two alternative stations cannibalizing each other.