Also just for fun, and since I like making lists I made a little list of what properties that have been brought up in terms of likelihood (with a one or two of my own I've considered)
Very Likely:
-Halloween (2018). Due to Murdy's tweets, HHN's history with the franchise scoring high, and Murdy's relationship with Jason Blum this seems nearly definite.
-AHS: Asylum. While some may argue that this isn't worthy of a "very likely" spot, I still see it as being up there due to Murdy's interest in the season in the past, and if this is AHS' last year, they have to go out with the most fan requested season so far.
Likely:
-IT (2017). I remember right after leaving the theater thinking that IT was almost definitely coming to the event and that it would be a horrible decision to let this slip through their fingers, and due to what Murdy has tweeted in the past so long as WB lets them, I expect to see it this year.
-Stranger Things. This has also been highly fan requested since season one, and while it would be pretty hard to pull off effectively I have some faith it will finally make it this year.
-Trick R' Treat. I was gonna put this lower but because of what I've seen I think it really does have a fair chance of coming this year. Along with that tweet a few posts before this one and the fact that if he really did have to leave I could see him taking a stab at it. Hell-O-Ween could have also been seen as a warm up for it.
Unlikely:
-AHS: Cult. While the costumes would be fantastic and seemed almost made for this event, I don't think we'll see it this year unless they go with a season 2, 3, and 7 mashup which could be possible if this is AHS' last year. Still due to the inherently political nature of the season I could see them avoiding it.
-IT (1990). This was thrown around as a possibility for a while but I don't think Murdy would skip out on the new movie. The new one has enough relevance to general audiences to be recognizable now, but I think seeing it be so different from what the GP expect could cause lots of confusion. I only really see this coming if they really want to shoot for the nostalgia of older fans over the teen demographic they usually aim for.
-Classic Monsters Mashup. I would absolutely love this to come but I still can't convince myself it will. Unless Murdy has found a way to make the classic 30's and 40's monsters scary to a new audience, I think this will remain a "what if", though I would be ecstatic to be proven wrong.
-Nightmare on Elm Street. I think this is way more likely to show up on the east coast than the west, since they haven't seen Freddy solo since 2007 but the concept of a NoES terror tram does sound intriguing to me, but I would much rather have an original concept on tram again, or just something we haven't seen before.
Very Unlikely:
-The Thing (1982). I would LOVE LOVE LOVE to see The Thing come to HHN this year or any year for that matter, since I'm a pretty recent fan of the event and only experienced the 2011 Thing in video form but I don't think we'll ever get to see this one through unless NBCUniversal starts taking a liking for this event and gave them a way higher budget. No matter how likely it is, this will always be my dream maze.
-Insidious: The Last Key. I don't think we'll see the fourth installment of the Insidious movies come to this coast just because it seems like since they cut so much out, there really isn't a huge amount of maze potential left. That and a good 75% of last year's maze was Chapter 4, which pretty much satiated my hunger for it. Also there hasn't ever been an Insidious maze based solely on one film, and there's probably a good reason for that. *cough* filler *cough*
-Happy Death Day/HOB Vol 2. I lumped these together because there have pretty much only been rumors pointing towards a second Horrors of Blumhouse maze rather than a solo Happy Death Day maze. I partially added Happy Death Day as a joke, and partially because it made plenty of money and would be fairly easy to pull off, along with GP recognition. It may be a little to similar to Halloween in terms of scares though. I suppose this could be swapped out with a solo Sinister maze if you're so inclined. A second Horrors of Blumhouse is possible, but it would pretty slim in terms of the choices to make into sections of the maze without using The Purge as a crutch. Maybe in a few years once Blumhouse has a few more movies out.
TL;DR, Halloween and Asylum probably coming. IT, Stranger Things, and Trick R Treat maybe. Cult, IT miniseries, Classic Monsters, and Nightmare on Elm Street probably not. And The Thing, Insidious 4, and Horrors of Blumhouse 2/Happy Death Day almost definitely not. (Sorry for such a long post)