Assad has the edge now in the war, and only a seriously unexpected event could change the vector:
The Assads depend on both Iran and Russia for the unexpected comeback from certain defeat. Iran has been backing Assad since the 1980s while the Russians largely stopped supplying Assads with much material aid after the Soviet Union dissolved in 1991. The Russians returned in 2015 and the air and tech support put the Assads on the road to victory.
Perhaps in the long run, Assad is doomed. But "history" doesn't tell us that Assad had to lose this decade--or the next one or the next generation (or the next Assad at some point in the future).
Early in the war I noted what Assad had to do to have a chance of winning. And he appears to have gotten his whole new war (albeit not as a deliberate plan but as losing ground in combat, and so with far more casualties) bolstered by Russian and Iranian intervention plus American supplied cash via the amazingly inept 2015 Iran nuclear deal.
And let me add that the survival of the minority Alawite regime demonstrates that the people who thought the Saddam minority Sunni Arab regime in 2002 was doomed to lose against the majority if America would just stay out and avoid "tainting" the Iraqi opposition.
Violence isn't over in Syria. Nor is opposition ended. Idlib province in the northwest has the bulk of the rebellion. There are pockets in the south although those seem to be getting ready to give up. And in the northeast the Kurds who want independence or at least autonomy from Assad (remember, I long noted that the Syrian Kurds would never be the core of an anti-Assad rebellion to march on Damascus) hold a large amount of territory; along with American-supported Arabs east of the Euphrates River who don't want to submit to Assad's rule (so what do we do post-ISIL there?).
So there is room for a "black swan" event to change the pro-Assad vector.
Syria would be better off if the rebellion had been "tainted" by association with America rather than figuratively inviting foreign jihadi ideology to fill the vacuum left by America's decision to do just enough to look like we are doing something yet not enough to prevent the spiraling casualties, massive refugee problem that eventually shook Europe, and the opening for Russia and Iran to entrench inside Syria.
Ah, nuanced Smart Diplomacy.
