From IMDb:
"Ledger played iconic comic book villain the Joker in The Dark Knight, the sequel to the 2005 film Batman Begins, opposite fellow I'm Not There star Christian Bale. The film is set to debut on July 18, 2008. Since The Dark Knight was in post-production at the time of Ledger's death, the film itself will be unchanged, although the marketing campaign that centred [sic] on Ledger's character may be affected."