If the division is on the line, the Bengals game will be flexed to Sunday night. The league doesn't have to announce the week 17 flex until 6 days before the game.
Like last year, Baltimore/Cincy and Pittsburgh/Cleveland were not flexed as they wanted to keep from the 4:00 game being meaningless... I don't expect us vs Cincy or Baltimore vs Cleveland to be flexed, IMO..KC seems more of an option