n LEO IN LONDON: Are Leonardo DiCaprio and "Gangs of New York" writer Kenneth Lonergan set to team up again? The buzz in London is that DiCaprio and Tobey Maguire will replace Matt Damon and Hayden Christensen in the West End production of "This Is Our Youth." The play, written by Lonergan, follows the fortunes of three rich, young New Yorkers during 48 hours of drug abuse and hedonism. It closed at The Garrick Theatre in June, but could reopen in October or November. A producer for the play, Clare Lawrence, would not confirm or deny the reports.