And they revealed the final boss at the last moment. Yes they could indeed do a second season but I doubt they would. The anime was good, very good IMO but if it ain't selling stuff then there is no profit for a second season.
Sickens me to know that stuff like Zero no Tsukaima get a second season for its fanservice but no continuation for better shows. Even Kage Kara Mamoru was better than that.