Board Thread:Manga/@comment-5774380-20160408232143/@comment-26095689-20160503045142

Tausendberg wrote: Season 2 is gonna be even crazier than Season 1 from what I hear. Supposedly the director is currently holding off on work on Season 1 until the manga is completely finished which leads me to suspect that the entire rest of the story will be squeezed into Season 2. You should read this http://attackontitan.wikia.com/wiki/User_blog:Manuel_de_la_Fuente/Attack_on_Titan_Season_2:_release_date,_facts,_rumors,_and_everything_we_know_so_far

Point 4 answers this

Supposedly the director is currently holding off on work on Season 1 until the manga is completely finished which leads me to suspect that the entire rest of the story will be squeezed into Season 2.