This is projection: the nations whose economies are solely based on oil, will be going back to caves when their oil is either depleted or otherwise made impertinent.
I wish I could find the quote, which came from a Saudi prince I think, and went something like “Before oil, my grandfathers were herders; after oil, my grandsons will be herders”.
Without diversifying before it’s too late, I think that prince might be right. (Notwithstanding climate change issues, and how brutally hot it already gets there.)