Five Nights at Freddy’s [official site] creator Scott Cawthon has confirmed that while there won’t be a fifth game in the main series – “the story is complete” – there will be another FNAF game soon. It’s an RPG:
“The new game that I’m working on will be called FNAF World. It will not be a horror game, but a role playing game where you create a party using the huge selection of characters from the FNaF games, including the classic, withered, toy, phantom, and nightmare versions.”
Cawthon had planned to release a demo in time for Halloween but the game’s “significantly larger” scope means that won’t be possible. There will be a demo, however, as soon as possible.