We’ve heard rumors about who might be stepping in, but now we’ve got the names verified. Count on it.
I'm actually kinda surprised Brad Pitt isn't in the mix, since he gave what's been--by far--the best performance of his career in Gilliam's 12 Monkeys. Depp's not much of a surprise since he's reportedly been wanting to work with Gilliam again since the ill-fated demise of The Man Who Killed Don Quixote (see Gilliam curse, above). Farrell and Law are both unexpected, but interesting, additions.
How is this going to work, you ask? Three additional actors playing Ledger's character doesn't seem possible, unless you do something odd like they did with I'm Not There, in which different actresses and actors played Bob Dylan through different phases of his life. Fortunately, this is a Gilliam movie we're talking about. Reportedly in the film, Ledger's character falls through a magic mirror/portal at various points, and different aspects of his personality are emphasized each time. Hence, different actors will represent these different aspects of character. It sounds kinda cool, actually. I hesitate to say it will be a better movie because of the change, but it will most certainly be a higher-profile movie because of these alterations and additions. Gilliam's in desperate need of a hit on the order of 12 Monkeys to ensure that he's able to keep making his wonderful films, and Ledger is in need of a fitting capstone to his too-short career. Hopefully, this will be both.