I think this Strategypage assessment of the Syria war is fair:
As of mid-2017 the Shia (Iran and ally Russia) are winning, but not decisively.
At some times Assad has been losing and at others he has been winning. Bolstered by Russian and Iranian direct support and helped by America's war against ISIL, which had been Assad's most potent threat, Assad is currently winning.
But "winning" does not mean Assad has "won." The battlefield trends are simply going Assad's way right now, even as the price Assad's side has paid continues to climb.
Once ISIL is defeated, and if America subsequently turns its focus on defeating Assad, Assad will no longer be "winning" as rebels who can no longer join ISIL join rebel groups that don't attract American wrath (and smart bombs).
And without the threat of ISIL largely crushed, whose threat kept Assad's supporters in line, perhaps those domestic supporters will start to think that even more deadly sacrifice for Assad's safety is a mistake.
Even if America didn't have an interest in destroying the Assad dynasty for a long record of killing Americans via proxies--from the Beirut Marines bombing in the early 1980s to the Iraq War insurgency when Syria funneled jihadis into Iraq to kill Americans (and even more Iraqis, of course)--America has an interest in either defeating Iran and Russia in Syria or increasing their cost of involvement in propping up Assad.
Just keeping the Russians and Iranians busy in Syria rather than letting them focus on a more important region is important.
The war isn't over until it is over. Work the problems.
