The Arab world's remaining eight monarchies have so far managed, through fair means and foul, to head off popular pro-democracy revolutions that erupted in January 2011 and ousted the dictators of Tunisia, Egypt, Libya and Yemen, and may yet bring down Syria's embattled president.
But, as Robert D. Kaplan of the U.S. global security consultancy Stratfor observed: "King Mohammed VI of Morocco, King Abdullah of Saudi Arabia, King Abdullah II of Jordan, Sultan Qaboos bin Said of Oman and the various sheiks of the Persian Gulf are ... more nervous on their thrones than a few years ago: in particular the monarchies of Jordan, Bahrain and Saudi Arabia.
"Moreover, they are not angels. Strong and regularly ruthless security services help keep these monarchs in power. Nevertheless ... compared to other regimes in the region, these monarchs have been both enlightened and Machiavellian in the best sense of the word."
Many in the region saw the abdication of Qatar's 61-year-old modernizing emir, Sheik Hamad bin Khalifa, 61, Tuesday and the handing of power to his British-educated son, Sheik Tamim, as a signal to other royal rulers in the gulf, most of them in their late 70s and 80s, that they should give way to a younger generation.
The Arab revolutions were largely driven by young people, the digital generation that demanded a future, reform, employment, and underlined the growing age difference between rulers and the ruled.
According to the World Bank, 70 percent of the Arab world's 400 million population is less than 30 years of age. They're no longer willing to be suppressed by secret police or bought off as their elders were.
The rulers of the gulf petrostates are grappling with this problem, even while, led by Saudi Arabia and Qatar, they're arming Syrian rebels to bring down another Arab tyrant, Bashar Assad of Syria, an ally of their religious enemy, Shiite Iran.
But trouble is brewing in Kuwait, the only gulf state with a Parliament, Bahrain and the United Arab Emirates, and the signs are things will get worse.
These monarchies have survived recent upheavals in considerable part because they have a legitimacy and tribal tradition that the Arab republics, some of which like Egypt and Libya had toppled monarchies, do not have.
These dynasties know deep down that reforms are needed if they're to survive. However, by and large, they move slowly, and time is not on their side as the Middle East is convulsed by religious wars and turmoil that seem to herald a new order.
"The Qatari move is an important one," says Shafeeq Ghabra, professor of political science at Kuwait University. "It sets the bar higher and puts pressure on the rest of the region to put their house in order."
The big problem for the gulf's royal families is the advanced age of the ruling generation and potentially tricky succession issues. Saudi Arabia seems to be in the biggest mess.
The kingdom, the world's largest oil exporter, faces a potentially troubled transition if King Abdullah, who turns 90 this year, dies or abdicates because of the abundance of scheming princes who are his half-brothers, all in their dotage.
Two crown princes, who would have succeeded him, have died in the last two years. Saudi Arabia is still run by the sons of warrior king Abdel Aziz who established the kingdom in 1932, largely by the sword.
He had 43 sons before he died in 1953. Every monarch since then has been a son as the crown passed sideways from brother to brother.
Abdullah, increasingly infirm, is probably the last of those sons who'll rule, but so far there's been no sign that power will go to the grandsons.
"Over-dependent for its legitimacy on the reactionary Wahhabi clerical establishment, the House of Saud faces a succession crisis as an absolute monarchy without an absolute monarch, as al-Saud factions jostle for position," veteran Middle East analyst David Gardner said.
"Even Saudi officials liken it to the gerontocracy of the Soviet politburo after Leonid Brezhnev."