Look at the players with the most to lose. It is the Assad regime and the Kurds. They live in Syria, have the most political unity, military strength, and willpower.......and they live there, always have and always will.
The FSA and all the other minor players are joining and rejoining whichever side suits them today.
Russia isn’t going anywhere, they have a permanent air and naval base, that’s really all they want. They’ve already achieved their goals of keeping Assad in power, that’s not going to change.
Think about it, look at the restrained effort we are making against ISIS. Assad and the Russians have little to fear from us. The Russians will support the marxist element of the Kurds, even if they lose influence with the Turks.
Rojava will be a reality, covering every part of the former Syria east of the Euphrates River. Yes, I said the former Syria. It will be partitioned by common agreement between the US, Russia and the Kurds.
Iran is the only outside influence that is expanding. But Russia and Assad will keep them in line to a major degree. Iran will come to agreement with the Kurds about the natural gas pipelines they want to build to the Lebanese coast.
Kurds are good allies. Both to US and to Russia. Both of them want to have someone like Kurds to deal with in the Middle East.
All Kurds are not alike. Syrian Kurds are the best of the bunch.
My concern is, will the USA stick with them after our goals are met? We have had a bad habit of abandoning people in the past, and Turkey is eager to expand into this area. Rojava is already a defacto state, and Syria will accept that with pressure from USA and Russia. What will be offered to appease Turkey?
The McCain wing of the GOPe, the State Dept and the Saudis still love their Jihadis in the FSA, even though they would stab us in the back at their first opportunity (and would probably be worse than Assad). They will try to block or minimize an SDF/Kurd victory, as that marginalizes the FSA and preserves the Assad regime.