Smooth Jazz will return to the radio...probably never, or maybe on a smaller, suburban station. That particular format's demos are not as advertiser friendly as they were 20+ years ago. Plus you can't base whatever billing success there was of the smooth jazz format vis a vis the alternative/AAA/whatever it was rock format that followed. Also, in a market of 15+ million people (plus tourists/visitors to the area), there should be enough of an audience for just about any type of musical performance. Just because venues are packed doesn't mean there's a format that can be built around it.
Think of it this way with a (somewhat outrageous) example: Broadway shows, I'd think we'd all agree, are quite popular. Packed houses daily for the most popular shows. Granted, audiences have a larger mix of out-of-towners being a tourist attraction, but still...
Having said this, where's the "Broadway Show Tunes" format? Besides the one-day stunt on 105.1 FM New York many years ago?
Emmis made a calculated gamble that trying to reach young males would pay off more than the demos they were getting with CD101.9. They lost that gamble - plus Emmis as a whole recently was up against large debt payments in September. Thus the need to sell off majority stakes in 3 stations. As has also been argued here, perhaps 'RXP's rock format would have been dumped earlier if the station wasn't being sold off - no need to invest $$$ and effort into something they knew would be divested soon.
If the smooth jazz format had continued uninterrupted on 101.9, would Emmis had been better off today? Maybe slightly, but not enough to make a difference. Not just in New York, but the smooth jazz format is disappearing across the country - unfortunately it's not financially feasible to keep it as is - which is why some of them have morphed into smooth AC, if not abandoning the format altogether. Is there still a audience for it? Sure. Thousands of people in the NYC metro? Sure. Enough and in the right demos that advertisers like thus being viable financially? Apparently not.
As with any musical format, it's not a commentary on the quality of the music itself (although quality's an arguable point - it's in the ear of the beholder).