I mean, I agree the M3GANs should get a permanent spot if they (or a similar act) were to return, and it could be put by a FNAF house to promote Blumhouse, but there is no way they don't give a horror property as major as FNAF it's own house. With the pairings they've done in the past, neither movie had the popularity, anticipation, or generational appeal that FNAF has.I feel like its going to be wound up placed with M3gan, same situation as Freaky and Black Phone with M3gan starting the house first and fnaf being the ending. It would be a perfect opportunity to place the M3gans by the ride and give them a permanent spot especially to promote the house if it sticks to being by F&TF but I'm sure it'll still be a nightmare.
As for Freddy, he tends to pop up a lot often in the rumor mill along with the other slashers and its understandable since most people see the anniversaries coming and I don't see Universal always using anniversaries all the time to just bring the ip, there's been a few times yes but I'm not seeing them doing it as a constant thing but also you don't always need something to promote the house coming too.