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.
I think a major problem is that even they can't know who among them - in the big groups of refugees making the journey - is an isis member or supporter, and even if they're not, there's no telling who is going to radicalise in the future. The attacks earlier this year in paris weren't done by someone that came from that area, iirc.
The French TV mentions that the terrorists were speaking French. And based on previous attacks it is more likely to be home grown terrorists. Syria is probably just a pretext, like a lot of European leftists in the 70s were using the Palestinian situation to justify their terrorist attacks.
This is probably french terrorists, but they probably did this because they couldn't go in Syria or were ordered to do it in France from Syria. There is hundreds of young french men and few women who went there. There is every week in France a group of muslim terrorists that are arrested because they were ordered or prepared a strike. One time a group a 10 terrorists was arrested.
The problem is that there is a very significant portion of the French immigration who absolutely hate France and that ISIS can recruit so easily in this population. In many suburbs of Paris, people were cheering during 9/11. And earlier this year you didn't see any immigrant in the Charlie support demonstrations. The French press is trying to spin this as a foreign attack from the middle-east but I think that the real problem is inside France.