Sadly, the "Attack On Titan" Season 2 won't be happening soon as there's no official update released about it yet. But the good news -- the "Attack On Titan" prequel migh be released December of this year, according to Hallels.com
The prequel will focus on Levi's story instead of Mikasa and Eren. Some said this prequel is necessary for both season 1 and 2.
According to the source, the reason why no announcement was given yet regarding the release of AOT season 2 is because Wit Studio hasn't begun the production for the next season yet.
The prequel is a spin-off and its title is "No Regrets, Birth of Levi".
As mentioned earlier by Hallels.com, Attack On Titan prequel is set to release in December. Latintimes also reported the same release date.
The reason why production has not yet started is due to insufficient volumes of the Attack on Titan manga available which will then be used as the material to cover an entire season of the anime TV series, according to iDigital Times.
Aside from prequel, AOT will be having a live-action movie, which has been divided into two parts.
According to Hallels.com, the first part of, "Attack on Titan" is titled: Crimson Bow and Arrow, and will hit theaters on November 22. The second part title is Wings of Freedom, which will be premiered next year.