Technically three replacements as this is the last year for The Hollow scare zone. Now if they were to add a maze's closure to this year, I can see it being Dark Entities since The Depths is big enough (and more fondly looked at) to warrant getting an official farewell season. D.E. on the other hand, you could quietly close and I don't see many folks (if any) throwing a fit over it. Other ways to get new offerings would be a new overlay for the Log Ride, or perhaps building a new maze in a formerly used location such as the Bumper Cars.
I've got a lot more food for thought when it comes to 50th spec, but I'll save it till this season is actually over.