I heard they closed River County due to the fact that the water was fed from the lake, which contained bacteria which could be considered harmful to some people. They would have had to re do River Country so that the water fed into it was purified(to expensive) now they have other water parks (now it is redundant) so there was no need to spend money on River Country and they closed it. Rumors have gone round and round with plans for River Country, and someone even posted building plans which involved the land it was on, but nothing has ever been built and no project has ever been mentioned by big wigs. Still the love of River Country is so much for people that the rumors keep going, which is fine by me because it gives me a reason to remember my "ole swimmin hole". I d recall spending a lot of time in that bacteria infested soup and never had any problem from it, just another sign of how overly protective we as a society are becoming. everyone needs to be sterilized with hand cleaner, fed foods free of everything and play sports where everyone wins. Darwin would roll over in his grave if he observed this
I've heard numerous reasons and factors that ended up leading to River Country's doom and downfall.
1. The above mentioned issues with the main "swimmin' hole" sharing it's water with the lake.... ie. Sanitation, etc
2. River Country was the first onsite water park. In the decade before it's closing however, Disney had opened 2 new Water parks that were larger and offered more for guests in the way of attractions, food, etc.. As a result, River country ended up being the smaller, less 'thrilling', waterpark onsite, but still cost the same to enter.
3. Liability issues. Namely.... This was a water park that opened in the 70's. It had deep pools, Drop slides, and in the biggest section, murky lake water. In Today's litigious society it was a park full of potential legal nightmares.
4. Access. it was hidden all the way in the back of Fort Wilderness and therefore the transportation and parking situation for most visitors was a nightmare (compared to the other water parks which were located on main roads and had their own parking lots right outside the park gates).
5. And finally..... the final death knell......The Tourism collapse that followed 9/11. With the decline in Tourists visiting the resort in the years following 9/11 (the same one that led to the demise of Pop's Legendary Years), There was no reason to deal with the expense and trouble of keeping 3 on-site water parks open as there wasn't enough guests visiting Disney Water Parks to fill them all. Due to all of the above reasons, it was decided to just close River Country and focus on the 2 newer parks.
As for the ole' Discovery Island... i honestly don't foresee much happening with it. When AK opened it made the nature preserve of the island redundant, so they moved the animals from the Island to the AK Park.... and even took the Island's name and brought it to the new park to replace the Safari Village name. (the home of the Tree Of Life)
Now, especially with the increasing number of guests visiting the resort, I can't see any potential use of the island that would make the logistic issues worth it. It's a small, isolated Island which can only be accessed via watercraft. It's too small to house anything that would be a large draw. There are better locations for a small, upscale, Boutique style park or hotel... the property is large enough they still have isolated areas they could build something if that's the vibe they want, yet still have an easier time with the logistics of supplies. And as an island, In Florida.... they can't do an open beach for swimming (anymore), and the frequency of storms would make for unpredictable access when watercraft would need to be shut down for safety reasons.
I honestly think from Disney's standpoint, It just make more sense to designate the island as another "Conservation land" area than spend the money to bring it's infrastructure to the point that they could do anything with the area again. Since Disney pretty much controls the land use for their property, They can take this old guest area and do one of their land use trades to re-purpose existing Conservation Land to another use while maintaining their overall conservation land allotment the same.