As for my speculation.
1) AHS Asylum (FDTD Area)
2) Stranger Things (S747 Tent)
3) IT (1990 Version, Mummy Queue)
4) Halloween (JP Queue)
5) The Conjuring (Waterworld Queue)
6) Trick 'r Treat (Metro Sets)
7) Classic Monsters Mashup (Parisian Courtyard)
I would imagine that for marketing that they would want to market Stranger Things, IT, and Halloween (Maybe also Conjuring). Huge Properties to promote. I feel as though Classic Monsters would be our exclusive.
Halloween would work great as a Preview Maze and again Halloween is too big of a property to be put into a Mashup Maze. Is it possible? Yes but again I don't see it happening. Insidious got a Preview Maze and that's a Huge property so I can Halloween getting the same. The properties that were featured in 2017's Blumhouse like Purge, Happy Death Day, and Sinister all of those Properties's popularity doesn't hold a candle to the popularity of Michael Myers.