It's a bit early to be getting details about the upcoming sixth season of American Horror Story, but the rumor mill has sprung into action. The biggest one flying around right now is that the next season will focus on the story of the Slender Man, a now-famous character. If this turns out to be true, this would be the second 2016 series based on a creepypasta after SyFy's Channel Zero, the first season of which will be focusing on the Candle Cove story.
According to an Us Weekly source, “Someone else wrote the script, and AHS wants to adapt it to fit the show. They have to buy the rights. Then they’re going to figure out the cast from there.” Again, there's no solid confirmation on this tip, but if American Horror Story really did feature the child-stalking monster, it could be a story ripe with potential. Especially taking into account the widely publicized murder supposedly inspired by the Slender Man, there could be a lot of thematic depth to mine.
Hardcore fans might start poring over the final episodes of Hotel for a clue to the next season's topic, which showrunner Ryan Murphy has famously planted in every season to hint at the upcoming theme. Personally, considering that the hint for Hotel was apparently a top hat, I think he retrofits those clues to mean whatever he wants them to mean, but feel free to explore if you really want to!
The cast for the new season has not been officially announced, though Ryan Murphy let slip that Angela Bassett would be returning. Emma Roberts has also expressed interest in coming back, though that may not happen in the wake of the news that Scream Queens is getting a second season.