It seems there's a social convulsion every generation. 1914, 1939, 1964(ish), 1989 - a cycle that repeats about every 25 years.
I'm not going to get too numerological about this - the average age at marriage and/or first live birth varies over time - but I do wonder whether one important element in history is human physiology.
It's also odd that we speak of a "generation", as though humans bred en masse in seasons separated by many years, like cicadas. But I guess there's a certain age span between those just too young to have taken part in the last bash, and those just old enough to want to get into gangs and rumble in the next one.
Maybe Occupy Wall Street, St Paul's, Thessaloniki etc are just the pubertal stirrings of the next revolution, the quasi-Aldermaston-March preludes to the next mass mania.
2014, is my guess.