I predict cruise missiles and drone strikes. Somehow that is seen as a cleaner, nicer way to kill people. Then, when that half-measure doesn't work we'll starve the women and children of Syria for the next decade with sanctions until another gung-ho cowboy gets into the white house and just says **** it let's invade.
It is so much more complicated than this.
Here is a plausible scenario that I see:
America, with backing and support from France and Britain, strikes Syria with missile attacks over 2-3 days.
Syria and Iran, either directly or thru Hamas and Hezbollah, strike at Israel and embassies in retaliation.
Israel strikes back at Syria, Palestine and southern Lebanon, hard. It is Israel and they won't take half measures.
Syria declares war on Israel and Israel on Syria. Hamas, Hezbollah and Iran join Syrias side.
America provides logistical support to Israel. Another chemical attacks occours and America hits Syria even harder. Perhaps Britain bombs Syria.
Russian naval forces engage in a tense standoff off with American, British and French naval forces off the the coast of Syria.
Saudia Arabia and Qatar flood in war materiel to the rebels. Turkey goes after the Kurdish regions.
After continued fighting in southern Lebanon Israel and Lebanon declare war. Iran follows suit and declares war on Israel as well.
Iran attempts to close/mine the straight of Hormuz. American and Iranian forces directly engage each other. America and Iran declare war against each other.
Iraq, Phakistan and Afghanistan support Iran and flood in jihadi fighters, weapons and money.
Russia intercepts a western powers attack (perhaps missiles or bombers) on Syria and shots are fired.
Russia and the west declare war. NATO is pulled into the conflict.
China now has a chance to recapture Taiwan while America is distracted. Japan and China have a naval skirmish over the Daiyou islands. North Korea and South Korea engage in shelling and war is declared.
South China Sea fighting pits Australia, Japan, South Korea, Singapore and Phillipines against China, Cambodia, North Korea and now by proxy Taiwan.
Due to all the fighting and foreign fighters thru out the middle east fighting along the Pakistan/India boarder heats up.
NATO (28 nations including heavy weights America, Canada, Germany, Britian and France), Australia, Japan, South Korea, India, Phillipines, Singapore, Vietnam, Saudia Arabia, Qatar and Israel are now at war with:
SCO (6 nations including China and Russia), Pakistan, Iraq, Iran, North korea, Cambodia, Taiwan, Syria, Lebanon, Egypt, Hamas and Hezbollah.
This scenario takes places with forces that are already in place. With threats of action already made. Such as naval forces from America, Russia, France and Britain off the coast of Syria. Gun fights on the India/Pakistan boarder, Iran's threat to close the straight of Hormuz, rocket attacks on Israel from hamas and hezbollah and tensions and standoffs in the south china sea.
Obviously this is a worse case scenario where everything goes wrong but the stage is set gentlemen.
Can't we all just get along?