(WARNING: Please be advised that there are mild spoilers for Attack on Titan Season 2) Attack on Titan is one of the most popular manga series today and has already produced an equally popular anime series. But unlike other manga series that releases chapters on a weekly basis,
Attack on Titan or Shingeki no Kyojin in Japanese releases chapters on a monthly basis. It is because of this slower than usual rate that the anime will have longer breaks in between seasons. This is done in order for the manga series to stockpile more chapters and have more content for the anime to make and at the same time and avoid catching up.
On the other hand, if the anime chooses to release episodes and seasons on a faster rate, it will eventually catch up to the manga which will force the writers for the anime to create original content for the series and diverge from the manga it is based on.
This situation is common to animes and sometimes, fillers, episodes that don't contribute to the overall arc while having its own closed arc are produced. The Attack on Titan anime which mostly follows the events on the manga chooses the "wait strategy" and is the reason for the long break between the first and second season.
One of the questions that Attack on Titan season 2 will hope to answer is of the the Titan's origin and story based on a report from geek.com. In a leaked English version of the teaser, we see more clues on the Titans.The teaser (seen below) shows a priest that belongs to a religious organization who worships the walls used to protect the city from the Titans.
This is nothing new for manga readers as the manga is several arcs ahead and could see where the series is headed. Without spoiling anything, here are the possible reveals for the next season: another huge titan, identities of two titans and back stories for other members of the Survey Squad.
Release date information for the Attack on Titan season 2 have been contradictory. Rumors state of a February 2017 release but was later refuted by Inquisitr. The voice cast on the other hand confirmed its premiere on spring 2017 at reading event . But still, nothing is official. Stay tuned for more updates.