I know that the land directly south of Camp Minnie Mickey was intended to be Beastly Kingdom. I assume it would have also absorbed all of Camp Minnie Mickey as well. To use this land now, Festival of the Lion King would have to move or fit the new theme (or be somewhat out of place like Finding Nemo The Musical).
To access the area you proposed for South America would require quite the long pathway. It's almost more useful if they were to expand Kali River Rapids and build an Asian Safari on a smaller scope as Kilimanjaro Safaris (although there's room to do both of these on the other side of the access road as well). I think those two things are incredibly unlikely however which is why I keep suggesting using that for a nighttime show.
The best choice for a pathway to get to your proposed South America area would be to the left of the Maharajah Jungle Trek with the actual entrance to the path to the left of Flights of Wonder. The path would cross over a current access road and run alongside the train path. It would also be about as long as the path from Africa to Expedition Everest and there wouldn't be too much space for much of anything along the way. I suppose you could conceivably have this walking path talk you through long narrow animal exhibits but there really isn't a lot of room to work with.
http://www.wikimapia.org/#lat=28.3590737&lon=-81.5899175&z=18&l=0&m=b