Who will replace Simon Cowell on “American Idol”? Bookmaker.com, a leading online gambling site, has a line for those who want to wager. Piers Morgan is the favorite at odds of 2-1 (bet $1, win $2), followed by Sean “Diddy” Combs at 3-1, Quincy Jones at 3½-1, Kenneth “Babyface” Edmonds at 4-1, Simon Fuller at 6-1, Rob Stevenson at 6-1 and Russell Simmons at 6½-1. Cowell is quitting “Idol” to star in the US version of his “X Factor.”