The death of Saudi Arabia's Crown Prince Sultan sets the stage for an eventual generational shift in the ageing leadership of the world's top oil exporter, even if King Abdullah picks 77-year-old Prince Nayef to succeed him.
At stake is the direction of a US ally attempting to reconcile its conservative traditions with the needs of a modern economy and a young, increasingly outward-looking population. Saudi Arabia, which dominates world oil markets and holds profound influence over Muslims through its guardianship of Islam's holiest sites in Mecca and Medina faces turbulence in its neighbours and a confrontation with regional rival Iran.
King Abdullah appears set to appoint veteran Interior Minister Nayef as crown prince and heir, but his choice of a defence minister to replace Sultan, who died in New York on Saturday, may signal how the conservative Islamic state manages the transition to its future leaders.
King Abdullah, Sultan and Nayef have run the country since the late King Fahd fell ill in 1995, but the monarch is in his late 80s and has spent three months abroad this year recovering from a back problem that again required surgery last week.
He remains firmly in control of the kingdom, but the focus will increasingly fall on Nayef and some younger princes.
Chief among them is Prince Salman, the Riyadh Governor who is a full brother of Sultan and Nayef and is seen as next most important in a ruling family that has prized seniority since it was founded by King Abdulaziz Ibn Saud in 1932.
"This all points to the key role of Prince Salman, who sooner or later will move up to crown prince," said a former diplomat to Riyadh who wished to remain anonymous.
"He will be the one who really decides whether the succession will stay horizontal among the sons of Ibn Saud or go vertical to one of the grandsons."