Older cities like Cleveland, for example, can still support classic hits stations that are still 60s-heavy, to some degree. But for the most part, the era of 50s/60s oldies on the radio is fading away, outside of small AM stations or "True Oldies Channel" outlets. And you'll be lucky to find a station that uses "oldies" in any part of their branding.
Regarding WCBS-FM, the smartest thing they could have done after the Jack FM flop was to reset the station back to what it was pre-Jack. And since then, they've been updating themselves continuously. Also look at "K-Hits" in Chicago, a 70s-80s classic hits station. And the 1980-2005 era "Gen-X Radio" (interesting concept, don't care for the name).
That's where the future of the format ultimately lies. One wonders why the format didn't update itself quicker over the past 20 years, unless if it was simple fears of giving up the 1960s era of music completely... and the attachment factor associated with that decade.