There are three theoretical possibilities:
1) Some amicable solution that ends the violence and allows life to continue as before. Probability: negligible.
2) France responds with enough force to end this riot and to deter future ones. Probability: Very unlikely.
3) France "pulls out" of the Islamic neighborhoods, creating their own little Gaza strip surrounding their capital. Life continues as France-under-siege. Probability: Almost certain.
I think Solution #3 is already underway. There are already some Muslim neighborhoods where even the police refuse to go, and there are virtually no city services there because other city employees are too afraid to enter them. I think you're right on the likelihood of the French simply expanding and making official the establishment of a separate "Muslim zone."
Sadly, I think that even if they were inclined to respond as in your Solution #2, there'd be so much international (read EU and Muslim countries) pressure on them that they wouldn't be able to do it effectively. I've already seen whining in the US press, which is barely covering the incidents, to the effect that it is all the fault of the French for not being nicer to their "immigrant" population.
Some immigrants. Invading army would be more like it, and to make matters worse, the invading army is being funded almost entirely, from cradle to the grave, by the French taxpayer.
Tell every blessed one of them that the money tap is being shut off to every person who lives in France, but liberal welfare payments are available to all who go back to live in their countries of origin.
France is going to be cutting the checks anyway. Why not send them to Algiers?
Unfortunately, France has nukes and I believe, several nuclear power plants....which present troubling possibilities.