Philip Jenkins says:
Alarmist pundits prophesy that a secular Europe risks being overcome by its fast-growing Muslim population. Yet for all we hear about Islam, Europe remains a stronger Christian fortress than people realize.
He points out that "new religious currents have become a potent force."
Examples include movements such as the Focolare, the Emmanuel Community, and the Neocatechumenate Way, all of which are committed to a re-evangelization of Europe. These movements use charismatic styles of worship and devotion that would seem more at home in an American Pentecostal church, but at the same time they are thoroughly Catholic. Though most of these movements originated in Spain and Italy, they have subsequently spread throughout Europe and across the Catholic world. Their influence over the younger clergy and lay leaders who will shape the church in the next generation is surprisingly strong.
Jenkins identifies various Protestant movements, and then invites us to pay attention to the "hugely energetic immigrant congregations."
On a typical Sunday, half of all churchgoers in London are African or Afro-Caribbean. Of Britain’s 10 largest megachurches, four are pastored by Africans. Paris has 250 ethnic Protestant churches, most of them black African. Similar trends are found in Germany. Booming Christian churches in Africa and Asia now focus much of their evangelical attention on Europe. Nigerian and Congolese ministers have been especially successful, but none more so than the Ukraine-based ministry of Nigerian evangelist Sunday Adelaja. He has opened more than 300 churches in 30 countries in the last 12 years and now claims 30,000 (mainly white) followers.
I don't have space to record all that Jenkins says, but he concludes this way:
Europe may be confronting the dilemmas of a truly multifaith society, but with Christianity poised for a comeback, it is hardly on the verge of becoming an Islamic colony.
All this is in line with his book God’s Continent: Christianity, Islam, and Europe’s Religious Crisis (New York: Oxford University Press, 2007). Interestingly, Richard John Neuhaus offered a major review in the May 2007 First Things issue. He has serious reservations about Jenkins' thesis and in his article explains why he remains expectant that Europe will eventually go Muslim.