User blog comment:Wahidkarzai/Series or Season?/@comment-179280-20131004181525/@comment-25358468-20140201020033

http://en.rocketnews24.com/2014/01/31/attack-on-titans-studio-head-talks-sequels-keys-to-the-hit-animes-success/

Good news! This states that there will "definitely" be a sequel to the first season.