The deathwatch for Fidel Castro is something that only Gabriel Garcia Marquez could get right. His novel “Autumn of the Patriarch” captures perfectly the moral squalor, political paralysis, and savage ennui that enshrouds a society awaiting the death of a long-term dictator.

Commandante Fidel’s departure from power, of course, will be solely a matter of biology, and the few pictures of him that have emerged since he took ill last year clearly show biology at work.

When the end comes, change in Cuba could be as vast as any that greeted the end of the last century ‘s great dictators. Joseph Stalin, Francisco Franco, Josip Broz Tito, Mao Zedong: All were mostly alike in their means and methods, but how they passed from the scene was very different, and these differences can shape societies for years and decades to come.

Consider the Soviet Union. On March 9, 1953, from the Gulf of Finland to the Bering Sea, everything stood still; likewise in Warsaw, Budapest, Prague, and East Berlin. In Beijing, Mao himself bowed before an immense effigy of Stalin. Huge mourning crowds, crying, nearly hysterical, could be seen all over the vast empire Stalin had ruled.

Yet, within days, the word Stalinism was being expunged from a new Soviet dictionary, and three years later my grandfather, Nikita Khrushchev, denounced Stalin’s “cult of personality” in his famous “Secret Speech” to the 20th Communist Party Congress.

The Khrushchev thaw that followed may have been short-lived, but for the first time in Soviet history the possibility of change was opened — a possibility that Mikhail Gorbachev seized upon in 1985.

The death of Tito brought forth an outpouring of another sort. For decades, his personal rule had imposed a false unity on Yugoslavia. Following his death in 1980, that artificial state began to unravel, culminating in the genocidal wars of state succession in Bosnia, Croatia, and Kosovo in the 1990s.

Not all long-term dictatorships, however, end in disintegration and mayhem. Mao’s death brought Deng Xiaoping’s return from disgrace and internal exile. Deng quickly routed Mao’s “Gang of Four” heirs, and in only a few years opened China’s economy, fueling a capitalist revolution that has transformed China far more completely — and successfully — than Mao’s socialist revolution ever did.

Spain, too, escaped violent dissolution when Franco’s fascist dictatorship collapsed at his death. Here the old dictator could take some credit, for by re-establishing the monarchy under King Juan Carlos just before he died, Franco provided Spain with a foundation on which to build anew. With the help of a clever young Franco-era bureaucrat named Adolfo Suarez, Juan Carlos built the modern, democratic Spain of today.

So what will become of Cuba after Fidel departs?

Many observers have portrayed Raúl Castro, Fidel’s younger brother and designated heir, as a pragmatist – the “practical Castro.” When Cuba’s lavish Soviet subsidies vanished in the early 1990s, it was Raúl who recognized that the regime’s survival required economic reforms, pressing to reopen private agricultural markets in order to boost food production and stave off possible starvation.

However, it was also Raúl who, as the head of Cuba’s internal security apparatus, for many years represented the knuckles of an iron-fisted regime, directly responsible for imprisoning — and often torturing — thousands of dissidents. So perhaps the best that could be hoped for is a Russian-style experiment with liberalization that is quickly called off by the regime’s nervous Old Guard.

Moreover, with the support of oil-rich allies like Venezuela’s President Chávez — and the recent discovery of significant crude reserves off Cuba’s own coast — reform could become less urgent. In that case, Raúl might cling grimly to the oppressive, fossilized system that he helped build and maintain with such brutality.

But Raúl Castro is an old man himself, so we should look further ahead to the prospect that some Deng or, better yet, a Suarez will ultimately emerge. For now, that appears unlikely: Younger communist officials, like Foreign Minister Felipe Perez Roque, remain ideological hardliners whom many Cubans refer to as “los Taliban.” If they assume control and stick to their guns, Cuba could face another long biology lesson.

Ms. Khrushcheva is a professor of international affairs at the New School in New York City.