What comes next in Iran vs. Saudi Arabia

Iran and Saudi Arabia's regional tug of war has shaped the Middle East for decades - think Iraq, Kuwait, Lebanon, and Arab Spring hotspots Syria and Yemen.

Saudi Arabia's King Salman is 81 and Iran's Supreme Leader, Ayatollah Khamenei is 78. What will the inevitable transition of power in these two influential countries — and historical rivals — mean for the region? We asked five experts for their perspective and predictions:

• Ali Shihabi, Saudi Arabia policy advisor, Arabia Foundation: Succession in Iran will escalate tensions
• Bernard Haykel, Middle East scholar, Princeton University: Don't expect de-escalation
• Dalia Dassa Kaye, political scientist, RAND: Youth will drive change
• Suzanne Maloney, Iran policy advisor, Brookings: Sectarian tensions are baked into the relationship
• Karim Sadjadpour, Middle East policy analyst, CEIP: The rivalry will grow