The current Russian-Iranian-Syrian-Iraqi alliance aims not only to fight IS in Iraq and Syria, but also to push it towards the border of the Saudi Arabia and supporting it against the Saudi Kingdom.
Russia has never forgot what Saudi Arabia did in Afghanistan in the reigns of Kings Khaled and Fahd when the Saudi Arabia offered the jihadists advanced weapons including "stinger" and shipped terrorists from all over the world to fight the Red Army. Those jihadists joined armies of ISIS later.
Rules of the game in Syria and Iraq are going to change. As the Soviet intervention in Afghanistan was one the main reasons for the collapse of the Soviet Union, the today alliance led by Russia is going to burn the Saudi regime.
Soon, the Saudi Arabia is going to pay for what they did to the Russian bear. The signs of the collapse of the Saudi regime will be crystal clear soon.
I believe that the largest cities in Saudi Arabia will witness horrific bombings that Al-Qaeda or ISIS will claim responsibility of. Time will reveal that several princes of the kingdom who are isolated from power are supporting al-Qaeda and ISIS to retaliate upon the King who ignored them and took over the throne with his son.