In an interview with Clash of the Titans director Louis Leterrier, FirstShowing.net recently discovered that there are 2 additional stories already written and ready to be filmed, making a Clash of the Titans trilogy possible. The director says that one of the conditions for Warner Bros to greenlight the first film was to provide them with a total of three. Obviously, parts two and three will not be greenlighted just yet, as the studio will want to make sure that the first film does well enough in theaters to warrant a sequel first.
But that shouldn't be an issue. BoxOffice.com is currently predicting that Clash of the Titans will bring in $70 million during its opening weekend.