The official settlers website has news that an expansion pack is on the way, expected in stores next month

The expansion pack extends the story of the original game with a fresh campaign, additional units and buildings, new gameplay features, a map editor and three exclusive heroes.

After Kerberos´ defeat, the Old Kingdom is led by its legitimate leader, Dario. His realm has regained peace since the evil attack of the Dark Knight and is prospering in harmony. But not the whole of the kingdom is peaceful. Rebellions have been reported from a construction site and one of Dario's closest companions has been murdered. A new danger appears clearly on the horizon, and once again it is Dario who has to fight for his heritage and the peace of his country's residents.