The immense popularity of "Overlord" Season 2 has encouraged Madhouse, the production house of the anime, to come out with the next season, and according to certain speculations, Season 2 will be aired in 2016.
My Anime List has reported that Season 2 will most probably get a spring release date as the online streaming service of "Overlord" anime has received overwhelming response from the fans and they have been constantly requesting for another season as soon as possible.
Some of the users from the forum also claimed that the manga version of "Overlord" has a lot of story that can be covered in Season 2 and even further seasons of the anime, given that Madhouse decides to produce it.
One of the users, Senpai, said, "Well it has enough source material and it sounds like it's selling well so there's a good chance it'll get one eventually."
According to When-will.net, though Madhouse has not yet renewed "Overlord" for a second season, the studio hasn't announced the anime's cancellation either. Hence, there is a significant possibility that "Overlord" Season 2 will see the light of the day soon.
Another speculation by Overlord Wikia claims that Lupusregina Beta – one of the prominent characters from Season 1 – will be returning in second season. Regina is a member of the "Pleiades Six Stars" – the battle maid squad of the Great Tomb of Nazarick.
Mathias Dante, one of the users of Overlord Maruyama Wikia, speculated, "The last episode of Season 1 seems to hint towards the end of a future season with Albedo's mentioning of the Lizardmen, the fortified Carne Village and Lupusregina Beta's presence there, foreshadowing to some of the events in Volumes 7, 8 and 9."
Another user from Disqus, Bow said that he is expecting more of Nazarick in Season 2.
"The second season will put some good efforts on politics between countries and Nazarick. I really want to see politics and financial and territory battles and struggles," he said.