The highly anticipated second season of "Attack on Titan" is now rumored to be the final season as well. According to a report from Design and Trend, this has to do with the fact that each season is designed to cover a certain number of chapters and that the manga should be four story arcs ahead before the season is released.

It was previously reported that the main reason season 2 has been delayed is because series creator Hajime Isayama wants his manga to be at least four story arcs ahead of the anime before the anime series is released, ensuring the reduction of filler episodes and to prevent the anime from diverting from the manga's intended ending.

This also plays into why the second season will be the show's final season. Design and Trend points out that Hajime Isayama's editor has confirmed that at the time of writing the manga series is roughly 60 percent complete. This would mean that there are approximately 27 volumes of the manga that have yet to be published.

"Attack on Titan" season 1 covered the first four story arcs of the manga, which comprises 34 different chapters. The report states that this means the remaining four story arcs that Hajime Isayama is still working on will include the remaining 40 percent of unpublished material. 

If season 2 were to cover the remaining four story arcs it will cover the whole remaining story of Isayama's manga. Given that the anime is being as faithful as possible to the original published work, it is speculated that there will not be a third season as this would require the anime studio to create their own story not based on Isayama's work.

Unfortunately, Isayama has not commented on the matter and until Isyama or Wit Studio releases an official statement, they will still be considered pure speculation.