Peaceful resolution of Syria is not Likely. Larger war is inevitable. The US has just upped the ante. To show to the World that America is great again, Trump wants to win in Syria, Iraq, Ukraine, Yemen, or where ever else conflicts start.
Of all the conflicts listed, Syria is the most critical, followed by the Ukraine. Bombing Syria for an unproven gas attack by Assad is a serious escalation. No investigation to prove who did it, just a claim without facts that Assad did it. A gas attack by ISIS or Al Nusra and then blaming Assad is more likely what happened. By this action the US seeks the removal of Assad and to partition Syria, which would immensely benefit Israel and possibly, the Kurds; Turkey would be a loser.
According to the Third Law of Motion: For every action there is an equal and opposite reaction. Assad will be reinforced by Russia, Iran, and Hezbollah. Iran might be willing to commit 50,000 troops or more and the Persians are tough fighters. To counter the Iranians, the US would be forced to commit an equivalent amount of troops. Would Congress allow this? Very likely. Why? Because Congress considers Iran an enemy of Israel, therefore, automatically an enemy of the US. Israel would attack Syria in order to fight the Iranians. Israel is already attacking Syria. Recently, Israel lost a plane over Syria. Hezbollah would join on a much larger scale than now in order to fight Israel.
Turkey is the wild card. If the US commits a large number of troops and allies itself with the Kurds, Turkey will expel the US from Incerlik and join Assad. The game would then be over. Will Turkey do that remains to be seen.
Another card that the US could play and will play is the Ukraine. The US would entice the Ukraine to attack Donbas, and Russia would be faced with two wars. For the Ukraine, Donbas is a hard nut to crack; it would lose all its teeth and lower jaw.
Iraq must also be considered as a very important factor. Iraq has a chance to be very powerful and an ally of Iran and Syria. The US is not eager for Iraq to take control of Mosul. If ISIS loses Mosul, the US would lose control of Iraq. Muqtada Al Sadar, the Iraqi Shia leader, will not allow any US presence in Iraq. Iraq will also help Syria.
Most likely the Syrian war will expand. The US may try to go for the kill with Israeli and Kurdish help. Turkish help would be better but may not be available. One thing is certain: big war is coming to the Middle East, and the winners are unknown at this time.
The losers could be the occult participants in the Syrian war. They have greatest interest in destroying the Syrian state and Assad.