As far as what format is "needed," yeah, there's not an obvious format hole in Chicago, and I would be surprised if Audacy flipped B96. But, just thinking about what Audacy would flip to if they decided to throw in the towel on B96, I could see:

* Classic Hits - they flipped a similar legacy station with lackluster ratings (KITS San Francisco) from alternative to classic hits. And Audacy has a lot of classic hits stations, so it's a format they're familiar with. On the other hand, they already had classic hits on 104.3 before they blew that up, and flipping KITS to classic hits hasn't been a ratings winner, either.

* Hot AC - it's another format they've tried before (on 105.9), but WTMX is no longer as dominant post Eric & Kathy, so maybe take them on while they're down? And with Hot AC, Audacy would still have a second female-friendly station they can pair with US99. It's also a format Audacy has had some success with in other large markets.

* Sports - moving the Score to FM would be another option. Audacy has moved several of their more successful AM stations to FM (WBBM-AM, KNX, WINS), maybe the Score will be next.