The editors of Mademoiselle magazine have peered into their crystal balls to see how well some of Hollywood's young actors will age. Kevin Costner will handle the years well and become his generation's Robert Redford, the magazine says, and Mel Gibson will be the next Paul Newman. A little gray around the temples will make Alec Baldwin "excruciatingly distinguished" and the next Clark Gable while Kyle MacLachlan's chiseled looks have a hint of Gary Cooper. But there's bad news for Sean Penn, who could be Marlon Brando in the making because "there's nothing alluring about a sullen 40-year-old," the magazine said, and Rob Lowe, who may be the next Roman Polanski once his looks go. There also could be trouble ahead for Tom Cruise, who Mademoiselle called the next Warren Beatty. "Here's a guy who is in danger of developing a Burt Reynolds complex," the magazine said. "At 28, Cruise's cocky air and toothy grin are charming. At 38, they could end up making him look a bit smarmy."