The following is all my own speculation. I have no inside info whatsoever.
So, a while back Scott announced that the next FNAF game has been placed on hiatus, not exactly canceled because he might come back to it. At first many fans (including me) didn't believe him because this fits his pattern of trolling the fans right before releasing a new game. Except this time that didn't happen.
First of all, it seems clear to me that Scott is not done with FNAF. There's the "Freakshow Baby" in "The Freddy Files." There's the Baby image on Scott's website. And there's the fact that the merchandise is still coming strong. If Scott really intended to wash his hands of FNAF, then the merchandisers would get off the FNAF train like rats off a sinking ship, otherwise they'd end up with tons of toys that nobody would buy.
Now, Scott has made all of his games in Clickteam Fusion. He's pushed the engine to its limits. And it is limiting. Scott