Looks like it may happen, although CBS doesn't say when. Lewis Lazare also points to the possibility of Emmis blowing up one of its FMs for sports, although I don't know why 3 sports stations would be necessary, even in a market the size of Chicago. It would certainly put pressure on WGN/Tribune and ESPN/Disney though, since neither owns an FM.
Link: Chicago Sun-Times
Link: Chicago Sun-Times