Well I assumed this was tied to the Lucasfilm acquisition but guess not. Variety is reporting that Disney has officially bought back the rights for the Indiana Jones franchise from Paramount:
The Walt Disney Studios and Paramount Pictures have reached a distribution and marketing agreement for the Indiana Jones franchise.This seems as if Disney may actually have a 5th Indy film up their sleeve if they went out of their way to reaquire the franchise.
Under the arrangement, Disney gains distribution and marketing rights to future films, in addition to retaining its current ownership rights which it secured when it acquired Lucasfilm.
Paramount will continue to be responsible for distribution of the first four films in the franchise and will receive a financial participation on any future films that are produced and released.