There is no end in sight for the Syrian War because both sides have a lot of fight left in them. This is due in part to the fact that losing is not an option for either and both sides are being financed by oil money.
What started as a civil war in 2011 quickly escalated in a sectarian war between Shiites, (Iran, Alawite Syria and Hezbollah) and local Sunnis aided and abetted by Saudi Arabia and other Gulf states and from time to time Turkey.
Almost from the start, President Obama backed the ouster of Assad by Turkey and some of the Gulf states with the intention of installing the Muslim Brotherhood to run Syria just as he installed the Muslim Brotherhood to run Egypt.
Victory was almost within the Sunni grasp until Russia entered the fray on the side of the Shiites and turned the tables. At some point along the way, Obama, in pursuit of the Iran Deal, backed away from original plans to oust Assad. This deal greatly strengthened Iran by giving it $150 billion and a license for seeking hegemony.
President Obama backed the ouster of Assad by Turkey...with the intention of installing the Muslim Brotherhood to run Syria just as he installed the Muslim Brotherhood to run Egypt. 
The conflict between Shiites and Sunnis dates back to a dispute over succession to Muhammad as a caliph of the Islamic community upon his death in 632. The dispute intensified greatly after the Battle of Karbala, in which Hussein ibn Ali and his household were killed by the ruling Umayyad Caliph Yazid I, and the outcry for revenge divided the early Islamic community.
Today at least 85% of the 1.5 billion Muslims in the world are Sunni, but the Shiites are concentrated in Iran, Iraq, Lebanon, Syria and Bahrain.
The eight year Iran–Iraq War was an armed conflict between the two countries lasting from 22 September 1980, when Iraq invaded Iran, to August 1988. The war was motivated by fears that the Iranian Revolution in 1979 would inspire insurgency among Iraq's long-suppressed Shi'ite majority, as well as Iraq's desire to replace Iran as the dominant Persian Gulf state. ( Wikipedia )
In 2003 President Bush removed Saddam Hussain from power in Iraq and attempted to transform Iraq into a democracy. The end result was that the majority Shiites were put in power and Iranian influence in Iraq dramatically escalated. This action, in effect, removed the most important bulwark in the way of Iran’s hegemonic ambitions.
In contrast, the Syrian War is in its 6th year.
The turmoil in Lebanon, Syria and Iraq can rightly find its roots in the Sykes-Picot agreement which Britain, France and Russia signed in 1916 believing that they would defeat the Ottoman empire in WWI. Essentially, in it, they divided up the spoils into three spheres of influence, one for each of them. When Russia withdrew from the war, it was no longer part of the agreement.
Due to the hue and cry that followed when this agreement became public, Sykes-Picot morphed into the more palatable division of the Ottoman Empire into Mandates, namely the Palestine, Syria and Iraq mandates, in which the ultimate goal was to usher in independence for the inhabitants of each area. No regard was held for the Shiite/Sunni divide, which was simply ignored. And thus we have sectarian conflict in Syria and Iraq.
Although Palestine was originally intended by the Mandate to be a Jewish state, Britain thwarted this goal by restricting Jewish immigration and encouraging Muslim immigration. And thus we have sectarian conflict in Israel. This conflict has resulted in many wars and has defied resolution.
For six years now the conflict in Syria and Iraq has defied resolution because there are no good choices.
Frank Gaffney Jr., in a recent interview in which the removal of Assad was the topic, said:
“The choices, unfortunately, seem to be more of the same. At best, it’s an Assad-Lite, supported by the Russians, supported presumably by the Iranians, supported by Hezbollah. Or, alternatively, it’s Sharia supremacists of the Sunni stripe supported by the Saudis, supported by the Turks, supported by perhaps al-Qaeda or the Islamic State, or simply the Muslim Brotherhood. All very bad choices, in my judgment.”
He did, though, support the creation of an independent Kurdistan in both Syria and Iraq.
“I personally think the President of the United States ought to be thinking about a Kurdistan in at least the parts of Syria – and maybe even Iraq or Iran for that matter – that are Kurdish, that have the opportunity or the basis for being safe havens for minorities that are currently very much at risk and are being helped by the Kurds.”
But what to do with the Sunni populated territories?
He worried that Trump would abandon his goal of defeating radical Islamic terrorism and its ideology.
“I think the president is now being buffeted by individuals who have come in who apparently do not agree with his priority of defeating radical Islamic terrorism, as he calls it, and who have, instead, the view that we should align ourselves with people who are the prime movers behind radical Islamic terrorism. That would include, by the way, the Saudis. It would include the Turks. It would include the Qataris and others in the region. I think that’s a grave concern.”
I share his concerns but have some suggestions to make.
At the beginning of the Syrian War, Turkey had visions of taking over Syria and recreating the Ottoman Empire. Why not play into that?
Let’s say, President Trump, the master of the deal, approaches Turkey with the following deal.
1.Turn from your drift to a 'neo-Ottoman jihad state' and reestablish the modern, secular nation-state of Turkey based on the reforms of Ataturak instituted in 1923.
2. Allow the secession of southern Turkey where 10 million Kurds live so they can have their independence and join the New Kurdistan if they so choose.
3. In return, the US will assist you in taking over the Sunni areas of Syria and Iraq and allow you to annex them if you so wish.
That would leave Alawite Syria as a state in which Russia could maintain its port and air field.
What’s not to like?
Turkey would get rid of a decades long insurgency and a financial liability and would gain far more territory than it gave up.
Russia would keep what matters to it.
The Alawites would have their own state and Assad would remain in power there.
Israel would share a border with expanded Turkey with whom they have normal diplomatic ties.
The Kurds would finally have a state of their own with a population of at least double Israel’s population.
America would have pro-American allies Israel and Kurdistan as bookends to the problematic areas.
And finally, Trump would have brokered the deal of the century.