I took this photo from Biorecontruct to show how little space there is between the left building and the coaster building.
If they want to develop the expansion I can imagine 1 large ip going in there (like LOTR). One portal has to be build between these structures and walkways. It could even have it's reveal moment when done smartly but dividing the plot into 2 lands would look very weird as you both have to go trough a long narrow area until the land actually can start.
Placing the portals back (also an option) would making them hard to find.
I'm confused about the design of this area. And than there is the problem of making the coaster invisible from both HTTYD and the expansion plot (if they actually want to go for a fully immerged 360 degrees "world" as promised.