It should come as no surprise that American Horror Story, the highest-rated series in FX's history, is being renewed for (at least) a sixth season, which will debut in in 2016. According to The Hollywood Reporter, co-creator Ryan Murphy has approached Lady Gaga, the current star of AHS: Hotel, about potentially returning. No word, however, on Jessica Lange, who has appeared in every season except this current one.
Since 2011, American Horror Story has tackled with murderous ghosts, grimy hospitals, demons, aliens, witches, traveling circuses, vampires, and dirty hotels — all of which are somehow part of the same meta-universe. That still, theoretically, leaves potential for future AHS seasons based around werewolves, mummies, zombies, the Loch Ness Monster, Big Foot, SEO optimization, more aliens, awkward social gatherings, cyborgs, or whatever that thing was in Kevin Smith's Tusk.