As long as people go to watch they are going to keep making them. These films spend very little to make and reward big. I see The Purge going to at least 5 films and Paranormal activity stretching it as far as 3 more films. Paranormal Activity's film series has spend 18 million on budget and have made over 800 Million Worldwide. That kind of money is just hard to pass. The last Paranormal activity made 86 million but even if the next one lowers to let's say 50 million, they are still making huge profit. Same thing with The Purge a ridiculous 3 million dollar budget and almost 90 million the the box office and the sequel is said to have been made with 5-6 million.