According to the Animagic 2014 report on ANN, George Wada announced that the production of the second season of Shingeki no Kyojin
has been decided. It is currently in the pre-production stage. The rest of the interview mentioned George Wada's experience with and interesting facts about animating the series. More information will be announced at a later time.
Shingeki no Kyojin 2nd Season