Allen has emerged as the best Vatican reporter in the English language. He is perhaps the only prominent Catholic journalist trusted by Catholics across the spectrum of theological opinion.

In The Future Church Allen outlines the major trends that he believes will shape Catholic life in the next century.

Allen tells us that what has dominated Catholic life for the past fifty years will change. Relations with Jews, for example, will take a back seat to relations with Islam.  He identifies ten trends that will shape the future Church. Of those, several underpin what Allen contends is the Global South's becoming the dominant force in world Catholicism.  He supports his claims with statistics, such as the projection that by 2050 seven of the ten largest Catholic nations will be in the southern hemisphere.  The Congo, Uganda, and Nigeria will be in the top ten. Spain and Poland will not. Uganda will have more Catholics than France or Italy.  As the archbishop of Boston worries about how to manage decline, the archbishop of Seoul struggles to keep pace with growth. The global story for Catholicism is growth, not decline, per Allen.

This demographic shift will change priorities in the Church. Debates of recent decades will give way to new issues of primary importance, leaving female ordination, priestly celibacy and other current issues dormant if not forgotten for a time.

Within Catholic worship and prayer, the Church will change, too, becoming more supernaturally focused.   Allen argues that the Church in the West became accomplished at dealing with the earthly powers arrayed against her. However, as the African influence within Catholicism grows, the world of evil spirits will inform Catholic spirituality to a greater degree.

Allen notes that the majority of the Islamic world is not Arab, and large parts of it (Indonesia, for example) have not been antagonistic toward Christianity.

The future remains in the future. The importance of this book is that what Allen predicts is already happening.