The Syrian war is entering a critical phase. Alliances are shifting but the goal has not and the goal is this: Partition Syria and remove Assad. The original proxy army of the US and Israel has not been too successful of late, but one cannot dismiss them. ISIS has proven that it has many lives; moderates and extremists.
The US support for ISIS is well known in the Middle East as is Israeli. Further cooperation will not bear much fruit. The US is betting now on the Kurds. If the Kurds obtain an autonomous area in the North-East of Syria, the area could become an anchor of US power in Syria and the rest of the Middle East.
The problem is Turkey. Turkey will not tolerate any autonomous region in Syria that is Kurdish, so the US finds itself between a rock and a hard place.
Turkey has been a faithful ally of the US since right after the Second World War. Also, Turkey has been a close friend of Israel. Most of the fresh water that Israel needs comes from Turkey. All three countries, US, Turkey, and Israel were, and possibly still are, supporters of ISIS.
The confrontation is increasing between Turkey and the US. Presently, Turkey is sitting on the fence. It is anchored in the West but wants to break free. This is a dilemma of historic proportions. If and when it occurs it will be a geo -strategically earth shaking event. If it happens, the US will be forced to leave Incerlik airbase. It is possible that diplomatic relations will be severed a la Iran.
Syria will shape the alliances of the region for years to come. Turkey has no choice but to side with Syria. This will guarantee Syrian unity and independence. The Kurds will have autonomy within a Syrian state. The US and Israel oppose such an arrangement, so more war is inevitable.
If this re-arrangement of alliances takes place, the end result will be as follows: Syria, Hezbollah, Iran, and Turkey will be backed by Russia and the opposing forces will be composed of ISIS, Peshmerga of Kurdistan National Government, the Saudis, the Gulf States, and Israel backed by the US.
If the US side wins though, the result will be as follows: Syria and Lebanon will be partitioned and Assad will be gone; water will flow to Israel from the Litani and Euphrates rivers; gas and oil will flow from the Gulf to Europe, decreasing EU dependence on Russian gas; a Kurdish republic will be established in N. E. Syria; Turkey and Iran will be weakened and, most important, Russia will be out of the Middle East.
However, if Syria wins, the following will happen: Syria stays united and much stronger under Assad; Turkey joins the East and its power is enhanced; Iranian power is enhanced as it becomes dominant in Iraq and Yemen and the Gulf; and most importantly, the Saudi dynasty will collapse, the US will lose the Middle East; Israel becomes totally isolated, and the Palestinians may rise up and win.
Whether the US will allow itself to be kicked out of the Middle East without a war remains to be seen.