Many were alive when the Soviet Union and the Iron Curtain fell. That makes such large upheavals believable. The weakness of authoritarian regimes is that by their nature dissention is hidden. Those in charge aren't really aware of how far they're overshooting until it's too late to release some of the pressure. I don't understand Chinese culture or their current situation enough to say whether or not they're in danger but Saudi Arabia certainly seems to have many parallels with other authoritarian regimes that fell to revolution.