Like most of the HoW are dead or in prison, there will be more heists, but with the Kell and Archon dead what is the point. There are bigger fallen threats out there than the imprisoned HoW. The main deal is the House of Winter and the House of Kings, HoK being the bigger threat but the DLC will probably consist of taking out the remaining House of Winter. Being that the disappearance of the House of Winter Archon/Prime Servitor is highly mysterious, not to mention their interest in the locked off portions on Venus.