Considering recent history , any country that gave up its WMDs was attacked (Iraq , Libya ) . Those who didn't were not ( North Korea , Iran even Syria so far ) . You make your own conclusions
WMD is only a deterrent if you can deliver it to cause maximum damage. Syria has no viable delivery system to use its WMD on western population centres, hell, there aren't even any western military bases in range to threaten, so if the US attacks Syria, what exactly can they do with their WMD to retaliate against the US?
Even if the US decides to invade Syria and put boots on the ground, those troops are all going to be packing NBC protective gear, so even if you dropped gas rounds right into their midst, it won't cause much in the way of casualties. On top of that, any use of chemical weapons on American troops would inflame US public opinion and effectively silence any kind of opposition against military action against Syria.
Right now, the need to secure or neutralise chemical weapons is the only excuse the US can dredge up to try and justify military action against Syria. If Assad turns his chemical weapons over to the UN, he kneecaps the US diplomatic cover, and the US would either have to back right off, or dispense with any pretence that military action is in any way shape or form justified and engage in naked aggression.
It is a good bet Obama is not willing to be so blatantly imperialist, and even if he is, Syria would have been attacked in any case, and as i have pointed out already, those chem rounds Syria has have no targets to hit, and even if there were, using them would only make things worse for Assad in any case. But if Syria disarms and America still attacks, Syria would find a hell of a lot more international sympathy and support than if the US attacked under the pretext of taking of chemical weapons. If Syria was attacked under such circumstances, Assad may even find willing allies in the form of the Russians and Iranians, who could send in personnel and equipment via backdoor means, just like the old Cold War proxy war days.