Just a heads up for some 'alluding' spoilers for The Purge: Election Year here. If you haven't seen the film and plan to, you've been warned.
Right, now those people are gone, I can say that The Purge: Election Year doesn't exactly end in a place where the franchise can really continue, or at least not in the way it has in the past. It had a pretty definitive end, with not too many loose ends. That is why the proposed The Purge 4 seems a bit odd.
Director/writer James DeMonaco recently spoke to CinemaBlend about how they could do it, and as you might have guessed, it's prequel territory. While he said he doesn't want to direct the next film, he says he would like to produce and or write it, and here is the angle he wants to take:
I don't think I'll direct it. I would actually go back and I would try to talk about how it all started. That seems the natural next chapter in this, is to say, 'Alright, we've done this trilogy. We see how it got to this point of someone trying to end it – this presidential figure. Now let's go back and see how the fuck all this came about.' How did this country get to a place where we were now accepting this kind of atrocity, this terrible thing, each year? I think there's something interesting in that. I don't think I'll direct, between you and I. You can print that, I mean. I'm thinking of maybe writing or at least producing it, to make sure it stays true to what I like about the movies.
If this franchise does have to continue, this makes total sense. There is almost defintely a story in how such a fantastical piece of legislation got to pass. I'm not sure how that is a horror or thriller movie, but like I said, I think there is a story in it.