"Attack on Titan" season 2 has been delayed due to the studios prioritizing "Kabaneri of the Iron Fortress" first but the second season is indeed in development. According to Vine Report, it is possible that the second season will reveal the origins of the Titans as this has already been hinted at with the previous teaser clips and the manga.

According to the report, the previously released teaser clip, which revealed the characters discovering larger Titans trapped and asleep inside the city walls, indicate that there may be a strong connection between the Titans and the current human civilization.

With the addition of the fact that the royal family members can all shapeshift into Titans, it is highly speculated that the Titans and humans are strongly connected. Ymir is also shown to have some connection to the origins of the Titans but this exact origin has not yet been revealed in the anime nor in the manga.

In a report from Crossmap, it is also speculated that at least one of the main characters will be killed off. As stated, the three main characters are Eren, his sister Mikasa and their friend Armin. While Eren has shown the ability to transform into a Titan it is widely speculated he may be killed off before season 2 is over.

A previous report stated that season 2 will also involve a rebellion against the royal family, likely due to their connections to the Titans, and it may be during this war that Eren or another major character dies. 

No official release date has been set for "Attack on Titan" season 2 but with the delay due to "Kabaneri of the Iron Fortress," it is now believed that season 2 won't be released until early 2017. However, this will allow the manga to complete its run, guaranteeing that the anime faithfully adapts the story without the need of adding filler episodes.