Breakout stars such as Michelle Dockery, Laura Carmichael, Jessica Brown Findlay and Joanne Froggatt have all had movie offers following the award-winning success of the British period drama, according to The Mirror.
Sources have told the tabloid newspaper that the young female cast members "know they can achieve more money" by leaving the show to work in films.
It was previously reported that Dame Maggie Smith wasn't signed on to return for a fourth run as the Dowager Countess of Grantham, but creator Julian Fellowes has insisted that he will never kill off Smith's character and that he will do everything he can to keep her on the show.
The 16-time Emmy-nominated show's third series, which will have the background of the Irish Troubles and a central storyline about the financial difficulties of the Crawleys, starts in the autumn on ITV1. It will air on PBS in the US on January, 6, 2013.
US star Shirley MacLaine, Matt Milne, Cara Theobald and Lucille Sharp are among the additions to the show's cast for the new series. Twilight star MyAnna Buring is expected to appear in the Christmas special.