Right after the Arslan Senki ending aired on Sunday, a CM ran revealing that a second season of Nanatsu no Taizai has been green-lit for 2016. You can watch the teaser here. The staff is exactly the same as it was for the first season, which aired back in October and was produced by A1–Pictures. It has not been specified whether this is a sequel or a whole new series.
While I haven´t seen Nanatsu no Taizai or ever really taken any interest in it, I´ve been told it´s actually pretty good for shonen standards, though the person who said this also hails Fairy Tail to be one of the best anime ever created, so I don´t know if I should trust his word or not.
One way or another, I´m sure the fans of the series are excited. It´s good to see a long running manga actually get adapted – though apparently the first season was rushed as hell and apparently there isn´t enough material for another two cours. Time will tell, time will tell.