Looking at the events history with replacing houses - it really is pretty up in the air.
HHN22 saw the last minute addition of House of Horrors
HHN25 saw Scream replaced with the Purge
HHN27 saw the Conjuring replaced with Hive
HHN29 saw (I forget... tooth fairy?) replaced with US
HHN30 saw Billie replaced with Case Files (though this was not as short term as the others)
So, unless I'm forgetting some, this gives us 2 outright IP replacements, 2 original replacements, and Monsters which while technically an IP is still considered a gray area by some.
This really could go either way. However, within the context of the currently speculated lineup I would wager that they would rather replace it with an IP if possible.
HHN27 still had The Shining, Saw, Blumhouse, AvED, and AHS
HHN 30 still had TCM, Beetlejuice, and HoHH and was also an anniversary year so Case Files truly worked as a replacement
This year currently stands as Halloween, Blumhouse, and the Weeknd - each strong in their own right, but not incredibly strong in terms of having a plethora of recognizable properties.
As it stands, I have no knowledge of what the replacement is / will be. However just browsing through Universals catalog I wouldn't be incredibly surprised to see: Chucky, Hannibal, the Thing or some variation of it, or even Krampus or the Purge again.