I believe everybody knew he'd be hit. There was testimony in Allie's trial from a DeCav captain, Gambino capo Mikey DiLeonardo, and others, all of whom had a suspicion that Cutolo would be hit ever since he began "strutting around" like the boss due to Allie's impending sentencing. Plus, DeRoss' behaviour shortly after the hit appeared to spark the suspicions of Cutolo Jr., even if it didn't immediately spark the suspicions of the rest of Cutolo Jr.'s family.
The only logical explanation for Wild Bill being unaware of his impending death is his closeness to DeRoss, and DeRoss' closeness to Allie. He must've been convinced that his best pal DeRoss had successfully bridged the gap between the Persicos and the Cutolo crew.
In fact, even in Cutolo Jr.'s tapes with Peggy and DeRoss and Barbara Cardinale (Wild Bill's daughter), Peggy makes references to how she knew Persico had ordered the hit, and DeRoss tries to diffuse it. DeRoss doesn't explicitly disagree with Peggy on the tape, he just tries to stress how he will take care of their family.