I didn't previously think revisiting the Nazis was worth doing, but I think there's merit there now.
I definitely don't want to see Indy spending much time in the Americas again, North or South, but it's the sort of thing that perhaps they could cheat, the way they've habitually blended legends of different provenance before, with varying degrees of success and truth-stretching: Egyptian and Judaic; a Kali cult plus Aztec sacrifice and voodoo; early Christian and the Crusades; and pre-Colombian, El Dorado, and aliens. Fate of Atlantis fudged the alleged location of Atlantis with a tenfold error, placing it in the Mediterranean rather than the Atlantic because it made for a better story.
So, maybe the rumors about Nazis in South America are a misdirect, just enough to draw attention from where they really are? But that would have the film playing with twentieth century facts in a pretty broad way that feels, to me, dicey. Are the Nazis hiding out in South Africa? Australia? Siberia? A minor string of islands somewhere in Indonesia or Oceania?