An interesting purchase for sure. I don't have much else to contribute beyond what is said, though I'm curious why 103.9 isn't being mentioned more in conjunction with the purchase. The other day, I heard 103.9 during their top of the hour bury their COL and finish their jingle with "WFAS, New York". I found that quite the departure from the Westchester positioning they've been using.
My exposure to Cumulus was primarily in Cincinnati and Youngstown markets, which, though they are very different demographically, give a small snapshot of what type of formats they run with. They seem to do quite a bit of rock, anywhere from old classics to edgier active formats. They typically have a news/talker, sometimes sports, and usually some hot AC.
My guess would be if WABC were to move to FM, the True Oldies Channel would occupy 770; however, I think WABC stays put where it is. I also think like some others that WPLJ gets even hotter, almost CHR, while 94.7 might fall on the soft side of a Lite FM so they could sell the two in combo. I also think WFAS may shift to a classic rock/hits format after they take over 94.7.
Just more speculation for discussion. Always a fun read with some of the regulars here...