Social science is far from exact enough to predict either eventuality with any confidence.

If waves of tens or hundreds of millions of refugees leaving places they cannot live in any longer begin sweeping across borders, how long will it be before fascist governments, already threatening, and already winning in Turkey, Poland, Russia, Belarus, the Philippines, Brazil, Hungary, Italy, and India take over generally and initiate wars, as they do? Such wars might not go thermonuclear, but they would certainly disrupt fragile global trade networks.