Meh, they're making over 3k a month. They'll have to cut back, and probably move out of their home, but between the sale of their home and downsizing, I dont see how they couldn't manage to live in the US. Add in the four kids helping out (if needed)..this is nothing but fear mongering and is a non-story.
Hell, I could retire tomorrow at 27 and move to a third world country and live just fine and dandy with limited income, just like the rest of the world does.
Granted, when I retire, I'm moving straight to Costa Rica.