Isn't this the one where they add time travel? Because if so my guess is that we are introduced to a new woman archeologist who knows so much more about history than Indy because all of it was done by black women who had all the credit stolen by white nazis and then she goes back in time and sets everything up so that young Indy can finish the early movies to the point that every success is really her success. And then they defeat "herr drumpf" or some shit like that.