Disney is not building another park in WDW so I don't know why they would need extra land.No they don’t. Ripping up wetlands has consequences. It alters the way water moves through the areas, and thus the flood plains.
If you’d like an example, the construction of Celebration made the WDW Resort more prone to flooding in a way it hadn’t been prior to its development.
Disney and neighboring homeowners getting in fights 20-30 years from now over flooding will make the Anaheim fights look like Rock Paper Scissors.
Plus, Disney could have used some of the not wetlands property for things that could feed the needs of the resort like more solar farms like the one proposed north of Flamingo Crossings and large scale hydroponics facilities to cut down produce costs.