Harry Potter may not be ready for his eagerly anticipated movie debut next summer. The Hollywood Reporter says that delays caused by Warner Bros.’ waiting for Steven Spielberg to commit to the project — he eventually passed — and the heavy load of special effects that the movie requires will probably force the studio to delay the release of the picture until Christmas of next year. The picture, based on J.K. Rowling’s top-selling children’s book “Harry Potter and the Sorcerer’s Stone,” will be directed by Chris Columbus (“Mrs. Doubtfire”). Warner Bros. executive Dan Fellman told the Reporter that hopes are high that “Potter” will still make it for summer — out of necessity. “Promotional tie-ins have been locked in,” he said.