Like all Disney decisions these days, this one comes down to the money. So, the leading candidates for the Island-formerly-known-as-Discovery are those ideas that make the most use of the existing resources on the island.
1. Disney's Dung Adventure: a return to Disney's edu-tainment legacy, this would be an interactive excretion experience. I won't spill all the beans on the interactive elements, but let's just say Epcot won't be the only place you can "Leave A Legacy..."
The current ad campaign is based on "Hey, there's some interesting crap, out there."
2. A wild mouse coaster, spinner ride, and carnival games will be dumped on the island under the banner Guano-Rama. This concept couldn't have been built within budget without the lucky (Magical?) finding of abandoned rides and structures that have already been authentically themed by flocks of pigeons and Canadian Geese.
3. To save on supplies and maintenance, the island will be converted to Pluto's Poop Pavilion, a one-stop solution for WDW guests' evacuative concerns.
All the other restrooms on property will be turned into churro vending locations.