First, let's define how many seasons of Owari No Seraph have aired till now. In fact, there has been just one season split into two cours subtitled Seraph of the End: Vampire Reign and Seraph of the End: Battle in Nagoya, accordingly. As a result, we are looking forward to the 2nd installment of the anime series, actually. This news may disappoint you, but, as mentioned above, there was only one anime season consisting of 24 episodes. Traditionally, in Japan, if the season contains too many episodes, a broadcaster prefers to split it into two parts, each containing twelve episodes. Thus, right now, I helped you to determine the proper situation concerning the number of seasons.
Another sad fact is that Seraph of the End: Vampire Reign has been included in the list of anime which Crunchyroll opted not to broadcast anymore. The announcement has been published in November 2018. However, this news more refers to the cancellation of the partnership between Crunchyroll and FUNimation Entertainment. Nonetheless, Owari No Seraph has appeared in the list.
As for the source material, the original manga as well as light novel series is still ongoing. However, the last chapter titled Seraph of the End: Guren Ichinose: World Resurrection at Nineteen has been announced as a spin-off series. One more time, coming back to the previous discussion, WIT STUDIO, Inc. or any other animation studio which might potentially produce another television adaptation is required the source material for 24 episodes (or at least 12). So, the producers are waiting for more volumes of manga.
Generally speaking, there has been no official announcement of the series cancellation. However, all the indicators point out this fact. I don't claim that the anime is being canceled. Everything may happen in the world of anime. We know a lot of curious cases when the show authors decided to revive the series. However, in the case of Seraph of the End, the odds are low. It's quite unlikely that we might see Owari No Seraph Season 3 in 2019.
However, I don't rule out that the anime could be revived. But still, in my opinion the series is dead and we won't see neither 2nd nor 3rd chapter of Seraph of the End on the small screens. It's doubtful, but there could be a spin-off series, which might adhere the light novel series storyline. Such a scenario is quite possible. But the release date of such a television adaptation could be announced only in 2020 or even later.
Seraph of the End SummarySeason 1 of the anime picks up right after the outbreak of a mysterious artificial pandemic, which wiped out almost the entire human population all around the globe. As a result, only children under thirteen managed to survive. Soon afterward, the endless hordes of vampires appeared on the Earth's surface, while waking up after the long-term dormancy, to reign over our world. The vampires conquer the remains of humankind. However, they grant safety for these people who can supply the vampires with the human blood.
The story centers on Yuuichirou, an orphan who has lost his fellow, Mikaela, as a result of the unsuccessful attempt to escape the Hyakuya Orphanage, where they lived worse than lab rats. Yuuichirou was the only survivor. Later on, he vowed to terminate all the vampires, while seeking revenge, to punish the guilty in his family's death. But subsequently, it turns out that Mikaela is alive. He is now a vampire, thus one of them whom Yuuichirou has sworn to eliminate.