This has actually been coming for decades. Even if it doesn't fully break out now, it's still coming. People here don't get it's Religion AND Race between these two. First of all, Shia-Sunni, of course. But, also Persian v. Arabs. Persians look down on Arabs, think they are dirty. And, the Arabs just hate the Persians right back. Not only that, you've got a power vaccuum in Syria and Iraq and the Iranians have heavily supported the fight against ISIS via the Iraqi Army and Iraqi militias. All of the sudden, Saudi Arabia could see a line of Iranian friendly states directly to it's North all the way from Lebanon to Iran. In the meantime, Yemen is a very distracting hemorrhoid drawing too much Saudi attention to the butt hole of the peninsula.