The original plans for WDW included a hotel in between the Contemporary and the TTC as well as a hotel on the North side of Bay Lake (near the MK).
Over the years there have been a number of reports of surveyors and ground testing crews at those locations, but obviously whatever might have been going on never blossomed into a new resort.
There have been a number of suggested resorts for Discovery Island - the best one I heard was a 'Hogwarts' castle!