Probably less speculation and more "what I want to see in 2018" but this is what I'm thinking.
Bring back the Scare Zones, for sure. Particularly in the Upper lot. I'd like to see the main one when you first come in, the tunnel and metro set zones, and bring back the one on French Street (I can't remember if that's the real name for it or not, but I think most of you know what I'm talking about). And maybe even a small scare zone or some wandering creatures on the Lower lot (around the escalators / mummy), though I can see where a full zone would be a total crowd flow nightmare on busy nights.
As for theming, I'd like to see Hollywood's take on Trick 'r Treat, maybe some rogue dinosaurs or experiments gone wrong in the lower lot, some original concepts (clowns?), I think It would be a cool fit for something in the Metro set, and personally I'd like to see a Purge zone return.
TWD: It'd be nice to see it possibly expand a bit down towards the Globe Theatre in a scare zone like fashion as you head into the Attraction queue itself.
Conjuring: Like others have said, probably in the Waterworld queue.
Stranger Things: I think ST is way too popular for it to not make it's way into the park this season. I could see them utilizing the area where Blumhouse was last year for this as it would give them places to come up with some pretty sweet concepts for both the woods and the upside down.
Twin Peaks: I'm not sure exactly how popular it really is, but I would love to see what they could do with this show. Most likely on the Lower Lot somewhere.
Evil Dead: Not sure the success of Ash last year (I liked it, but I don't get the feeling it was all that popular in general), but I think Ash is to niche of an audience to have a standalone maze. I think if they went for more classic Evil Dead, it'd be more popular and it could be really cool if done properly.
Simpsons: Since the ride itself is open during HHN, I'd like to see Treehouse of Horror incorporated somehow, maybe in an outdoor "queue" zone.
AHS: No doubt this'll probably be back again in 2018, either as a season standalone or a combined maze. I'd really love to see Asylum done as a standalone, but with the 5150 debacle at Knotts a few seasons back, who knows if they'll actually push for that. I can't see Coven or Cult being all that interesting as standalone mazes though. I preferred 2016's maze layout to this year's Roanoke, so I'd be fine with an Asylum/Cult/Coven combo too.
Halloween: Like others have said, I agree that we'll probably see a standalone Halloween maze this year, hopefully on the Metro/Lower Lot area where they can give it the space and facade it deserves.
Original Concept: The thing Knott's has on USH is their original concept mazes. I think OC mazes are popular themselves because people don't go into them with the expectation that they're going to feel like they're stepping right into the movie. I feel like IP mazes generally flop harder if they're not done right, no matter how popular their IP is.
Terror Tram: Classic Universal Monsters. As Disney's proven lately, the Nostalgia factor is HUGE. And I could see a Universal Monsters maze being quite a hit. Bring in Dracula, Wolfman, Frankenstein, Psycho, etc.
Live show- I think we're done with Jabbawockeez. I've heard rumors of their contract being up anyway, but either way, I don't see them returning next year. I would love to see Bill & Ted's reworked and brought back to Hollywood, especially now that it's finished it's run in Orlando.
Overall for 2018, I hope we see more of the old HHN. Less black hallways, less obvious scares, more theming and more monsters. With a lot of the construction that impeded the overall scarezones in 2017 finishing up (hopefully) before the 2018 season, hopefully we'll see more impressive scarezones this year.