There will certainly be many immigrants coming from the Third World that stick to their old values, but their children and children's children will drop them in time. Progress, even at the social values level, is inevitable and unstoppable. There need not be a shooting war.
Nobody can say that as though its fact. In France's case that country has a two polar opposites occurring at the same time:
On one hand the native French [white] population is rapidly declining whereas the Muslim population [which is almost entirely N.African] is growing by leaps and bounds due to immigration and very high birth rates from their immigrant parents.
This is something that has never happened before, we hear about how we in the US assimilated Italians/Irish in the past but it was different then. For one, the US White-Anglo population was not declining at all before the 1960s, infact it was the opposite. It was a booming population that was rapidly growing so there was little recourse for the Italians/Irish other than to assimilate...It was either that or become outcasts in their new country since the dominant culture was not going to go away anytime soon [atleast it appeared that way then, unlike today].
Nowadays of course things are different. The US anglo population is declining and its apparent to everyone that it is, and with it goes much of that culture. Hispanics have little reason to want to assimilate when they see their own culture taking over large parts of the nation [eg: Miami, much of the SW states]. France is in decline and Muslims are taking over parts of France as well, there is no incentive for Muslims to assimilate into Native French culture when the natives and their culture are on their way to meeting the dinosaurs.
And this is slightly off topic but look at a Globe sometime, France itself is tiny. Its about the size of the state of Pennsylvania...Any change in France is going to be felt by most of the population, Miami in the US is a hispanic city but it really doesn't matter since its just one city out of thousands. If a French city becomes majority Muslim it does matter. Marseille is going to be a majority Muslim city in the near future, and its just one of many French cities on the brink of becoming majority Muslim, the changes there are rapid and open for everyone to see.