Cash grab? you are comparing Call Of Duty a game that just by itself costs around 40$-50$ wich dont include dlc, to a game that costs 10$-20$ with no dlcs and telling me that the game is a cash grab when the fnaf 4 is the last game of the series, well there is something ilogical there.
Also i dont know why you are shocked for the teaser,so many companies do this type of things, not only gaming but for films or shows also it did not say it was the date for the teaser and if it is the date for it, the game normally goes on steam a few days later.
And yes some parts of the story was inspired by the comunity but not that much, Scott always gave hints for the story in all games for we to discover, also if the game was a cash grab he could just create even more controversy that would made Fnaf 4 just another game and not the final one, he could simply extend the series and grab even more money like COD does.