I doubt it. I found this picture while browsing on the Steam forums for FNAF 3: ( That is one of the ending screens. I believe it is the "bad ending", as they call it. ) This picture had the brightness put up, and if you look carefully: SPRINGTRAP SURVIVED THE DARN FIRE. Which means that there may still be more to the story. But who knows? Now, if you get the GOOD ending, I'm pretty sure you also get that picture, but also the "the end" screen with the animatronic heads. The kids' spirits are put to rest, the Purple Guy gets killed, okay got it. So there may not be another game. We'll have to wait and see.
I have a feeling that if Scott makes another one, it'll be like a sort of origins one, so like, how the animitronics came to be (Freddy,Chica,Foxy,Bonnie,Mangle, etc..) or maybe he may not ever make another one...
Huh, guys, do the math. $4.00 per game per device*tons of people+tons of people getting money off of it on YouTube+huge fan base+more factors=A pretty good game, I suppose.