Originally Posted by The Lone Raider
I've been working on a story since last December that would've been Indiana Jones 5 until they announced an actual Indy 5 movie. I initially had it take place in 1959 and with Mutt, but it has since been changed to 1961 and with all new characters instead. It would be believable to have it take place four years after Kingdom of the Crystal Skull, as Ford was 38 in Raiders and 47 in Crusade, though the two movies are supposed to take place two years apart.
So I would personally think that it would be the most fitting for the movie to take place in the early sixties, while it's still plausible for Indy to be active and still has a more 50s vibe like Crystal Skull.
I could go with '61. I just hope they do not set it any later than 1965.