I dont think they will intervene as
they cannot do a Libya, this requires 5 times the resources of Libya, and troops on the ground.
Air strikes will only knock out the air assests, and heavy armour of the Syrian army.
Seeing how badly they are using these assests, it think NATO will do them a favor.
With only a no-fly zone, I see a brief roll back of the Syrian army, followed by improved performance and defeat of the rebels again but on a narrower front.
This improved performance will push NATO into moving ground troops.
The reason why the Syrian army is performing badly is because they have not been listening to their Hezbollah and Iranian advisors on the ground. The changes required from them clashed with their political aims.
The Iranians advised reduced use of tanks and airstrikes, focusing them on smaller number of objectives, more intelligent use of infantry.
This collided with the egos with what remains of the Syrian general staff ..
Air strikes will see them shut the fuk up, and give greater control to Iranian specialists and competent Syrian officers.
But, I don't think Obama has the balls.