They made a mistake killing (spoilers)
Off nearly all The Strangers, cause alot of people liked this movie alot, better than the first movie, and they could have done alot of successful sequels on VOD with this. But with just The Man In The Mask left alive you can't really make anymore sequels.
I guess they could still do a prequel, but they would likely explain too much and show us who The Strangers are and completely make the title of the movies pointless.