2. It Will Be Half Prequel, Half Sequel
Over the years since Kingdom Of The Crystal Skull, a common idea for a potential fifth movie is that it will have a dual narrative. The idea goes that in the present or rather the 50s or the 60s Indy will uncover something that relates to an event in his past. Flashing back to the 30s or 40s, we would then see young Indy investigate said event. This would be a neat way to both bring back Ford for probably one last time, and to reignite the franchise with a new actor playing the role. This idea is even already being road-tested by the upcoming Die Hard: Year One. This direction does seem rather likely on paper, certainly if Disney are keen on turning Indy into a Bond-type actor-swapping hero. However, this would completely go against what Spielberg has said in the past, that the character would never be played by anyone other than Harrison Ford (ol Steven is apparently forgetting The Young Indiana Jones TV series and the fact that he himself cast River Phoenix as a teenage Indy). If Spielberg does really feel this way, then the likelihood of the fifth movie going down this path depends on how much input the man has into the future of the franchise, or whether the ball is entirely in Disney's court.