Who comes to the country with the sword will die by the sword, so was said in the Testament. It is just matter of time before London and Paris become like Lebanon - used to be 84% christian before muslims from all over migrated to it and started replacing natives.
If I am not mistaken, these cities are already lost. The Muslim population in London is close to 25%, and that city even has a Muslim mayor. The proportion in Paris and Brussels is even higher. The white flight has been going on for many decades in these cities.