With FNAF 3 out and many completing the game already, I believe the series has reached the end of it's story making it a solid trilogy. There's always a chance it could continue but the story indicates that it's probably the end. The following is what I assume to be the events of FNAF in chronological order.

First there's the first pizzeria known as Fazbears, where the first child is murdered by the Killer as seen in FNAF 2's minigame where you give cake to the children. After that incident the place shut down and another was opened but left to rot, whether the original Freddy, Bonnie, Chica, or Foxy came from the first or second I'm unsure.

Finally in FNAF 2 Freddy Fazbear's Pizzeria is open, with brand new animatronics that can detect child predators while the old ones sit in the back. Before this game the killer returns, using the Golden Freddy suit to lure children away to kill them, five in total and stuffed into the old animatronic suits in a restraunt before the one in 2 but not the one the very first crying child was murdered. However the spirit of the first child is imbued into the Puppet, and as seen in a minigame brings life to the animatronics with the souls of the other murdered children. The murderer using the Golden Freddy suit either tampered with or confused the new animatronics to the point they attack anyone at night who isn't a child or in costume, while the old animatronics do so out of revenge. Phone guy calls to confirm the killer used the Golden Freddy or Springtrap suit and that the place will close down due to the bite of 87 which was the year for that game. Whether it happened before or after the call is uncertain, but it is assumed Foxy bit an adult's frontal lobe off since the animatronics would never hurt a child.

In the first game we see just the original four animatronics after the newer ones were scrapped. They proceed to hunt down the player and even kill the phone guy. The restraunt was in the process of being closed down. At some point before that happens, the killer lures the animatronics one by one to him and manages to destroy them to protect himself. The spirit of the first child appears and along with the other four victims chase and corner the killer in one room with an animatronic suit that could be worn by humans. To escape, the killer jumps into a yellow Bonnie suit and laughs at their inability to go anything to him. But the springs in the suit were very unstable and as he laughs the suit suddenly snaps shut and crushes the killer inside, ending his life in an ironic way. The spirits dissipate but the story isn't over.

Finally in FNAF3 the pizzeria is gone but a haunted house attraction based off of the tragedy is now open. You play as a guard watching over the new establishment with no issues until management finds one animatronic still in one piece. This is Springtrap, the yellow suit that the killer died in, you can even see some flesh inside. The killer possessed the suit he was killed in and hunts you down, while you are plagued by hallucinations of the old animatronics. The good ending reveals that the place burns down as hinted by the guy over the phone, and the suit along with the killers remains are destroyed, endings his evil once and for all as the children's spirits move on.

A very interesting story, but one question remains: who was the killer?
Some say it was the Phone guy since you can see a badge and phone in one minigame, but he died on night 4 in the first game and the animatronics still pursued Mike on night 5 so it's unlikely.
It's more likely that Mike was the killer, though if he was fired before they got to him then that is also a problem.
All we know is that the killer had access to everything and though the newspaper articles say he was caught this is likely due to someone else being framed, possibly Jeremy from 2. It may even be possible that Jeremy and Mike are the same person under different names, making them both the killer and explains why the animatronics come for you.

My best guess for the killer however is the unnamed daytime guard in 2 that switched due to the animatronics coming for him during the day and reported no unusual activity while the place was being investigated. This gives him access to both the suit and his victims. Phone guy also states that the place is to be locked down and prevent previous employees from entering, as well as a new daytime position being open but that may be due to Foxy biting an innocent daytime guard.
But it isn't certain, this part is all just guessing.

But all in all this was a fun series with a plot that really made people think. As much as I liked it, I hope this is the end for story's sake with the killer turkey dead and the spirits in peace.

Any thoughts on the theories above? Did you enjoy the series?