NATO SAM batteries in Turkey, near enough to the border to knock down Syrian aircraft operating there, US talk about chemical weapon redlines, hints of troop deployments mean something is shifting in the West's approach to the Syrian government. No, I don't think it will be full on Iraq-type invasion but or a Libya-style air campaign. Syria is bigger and badder and actually has chemical and biological weapons which mean the potential for massive casualites among NATO troops should they get involved.
However, placing surface to air missiles in range of Syrian air force operations can have a dampening effect on those strikes. What I suspect is happening is a policy of forceful nudges with an aim to decisively tip the conflict in favour of the rebels.