I would say that there is virtually no chance of the US or the rest of Europe getting involved in Syria. They are not Libya, Assad and the Baath won't go down easily, and airplanes or drones by themselves are not gonna to resolve this. And- as we have already been told by the administration, in the future the US won't be doing "stability operations" anymore, so you know that we won't be doing anything to cause a "regime change" in Syria and without us being involved- nobody else will either. (Other than the Russians and the Iranians). Having served in Damascus for the UN - I feel reasonably confident in suggesting that their utility is slightly below zero- so I would say that the opponents of the Assad regime are in for a long, internal war in which they may get some covert assistance at most from the west.
We will be "Concerned" though