The repeated attacks, heavy immigration of refugees...I'm hoping for the best, but I feel like there is a powder keg here. Whether or not it is based in any fact, how this is handled and plays out is a serious concern.
France cannot really control the wave of migrants anyway. But it is unlikely that the terrorists are one of these migrants. My guess is that they were French nationals/residents.
There were eyewitness reports that the gunmen were talking to each other in French. So, that's something. If they were recently-arrived refugees that probably wouldn't be the case, though it doesn't rule out long-term embedded groups.