Given their half decent ratings and the broad base they probably cover, I'd doubt it. While both variety hits and
smooth jazz cover a desirable demo (age-wise), more people would be interested in variety hits than in smooth
jazz. Even if people hadn't discovered smooth jazz yet and might get attracted to it, rock/variety hits is
what more people would like to hear, in not just the desirable demo (age wise) but those younger and
older, too.
Look at a station like WBOQ--not exactly burning up the ratings, but suppose you're a salesman for them:
"We have a swing and jazzy format."
"We have 'good time favorite' oldies and AC (plus Red Sox and Celtics)"
Sure, the devotees of swing/jazz would feel it better serves them, but there are many, many more people
who who want something that's a cross between Oldies 103 and WROR (and they can run local ads
there at a cheaper rate, but still reach a coveted audience). And even if the ratings seem small,
they bill well. Or at least they're doing well enough that we haven't tuned in one day to find
"Smooth Jazz 104.9", or another specialty format.