Easily resolved with a five-minute short. Indy, circa 1969, wakes up from a nap before a press conference for a major archeological discovery (say, Atlantis), and it transpires that DoD was simply a nightmare. His son and grandchildren are there with him, along with his beloved wife Marion, to help him celebrate his wildly successful and popular career. Because nobody wants Miserable Indy.I agree that the Indiana Jones franchise needs to end at some point without needlessly wringing every single drop from it. But I believe that Indy and Marion deserve an ending where they find closure for losing their son Mutt.
Simple.