A 3rd gate really won't be a possibility UNTIL they can get BOTH IOA and USF in the top 10 in attendance in the world, until that happens, both of these parks will get a lot of TLC over the next few years.
However once the new hotel is built, that is a lot of land just across the street that could easily house a water park, whether its a completely new park or is the Wet N Wild land lease expires and they bring those slides over and add a lot of theming to them, but WonderSea Island should happen, its just a matter of WHEN not IF.
As far as IOA, Toon Lagoon theater definitely must be addressed as well as FFL, those 2 to me seem to be the next priority once they finish with TF, Potter, and Springfield.
Also, I think the land purchasing would be more offices, and behind the scenes reasons in order to free up more land on the main plot of land currently, just IMHO.