Pew Research Center report issued in April, 2015 projects the world religious population through 2050, globally and by country.  Extensive documentation, tables, etc.

The subtitle of the report is: "Why Muslims Are Rising Fastest and the Unaffiliated Are Shrinking as a Share of the World's Population."

In 2017, Pew updated this report as The Changing Global Religious Landscape -  at DataBank as 2010-2050 Projections updated
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Brief summary of data available in Press Release notes that:

"The religious profile of the world is rapidly changing, driven primarily by differences in fertility rates and the size of youth populations among the world’s major religions, as well as by people switching faiths. Over the next four decades, Christians will continue to make up the largest religious group, but Islam will grow faster than any other major religion. If current demographic trends continue, by 2050 the number of Muslims around the world (2.8 billion, or 30% of the population) will nearly equal the number of Christians (2.9 billion, or 31%), possibly for the first time in history.

With the exception of Buddhists, all of the world’s major religious groups are poised for at least some growth in absolute numbers in the coming decades. Atheists, agnostics and other people who do not affiliate with any religion – though also increasing in absolute numbers – will make up a declining share of the world’s total population."

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Report is part of Pew-Templeton Global Religious Futures Project.    Report is available for downloading via the Pew Research Center Study Page .  

Report organization:

• Summary Overview, pages 5-23 summarizes the report's findings.  Each of the following chapters add additional data and analysis.

• Chapter 1: Main Factors Driving Population Growth includes an analysis of the impact of fertility, life expectancy, age structure, religious switching and migration.

• Chapter  2: Religious Groups provides data on the main religious groups covered in the report, focusing on global numbers and geographical distribution patterns.  Data on Christians, Muslims, Unaffiliated, Hindus, Buddhists, Adherents of Folk Religions, Other religions and Jews [Jews-by-religion only].

• Chapter 3: Regions, provides a summary of current and projected future distributions of religions by world geographic regions.

• Appendix A: Methodology, Appendix B: Data Sources by Country and Appendix C: Defining the Religious Groups provide extensive technical/methodological discussions.

• Finally, Table: Religious Composition by Country, 2010-2050 provides detailed estimates of the total population in each country of at least 100,000 population for 2010 and 2050, as well as the estimated percentage within each country of the religious groupings identified in chapter 2.

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INTERACTIVE MAPS AND TABLES

Please note that the 2015 Pew-Templeton sponsored report also includes two interactive data analysis formats accessible via the Pew Research Center website and the links in this paragraph and on the left side of the Overview Page.

• A Data Explorer allows the user/researcher to ask and answer a series of questions based on the Pew data projections.  Previous questions asked by others are also included in the database.

• Also available at the Pew Forum site is a world religion table that can be sorted by year, by country, by religion; the excel file used for the analysis is also available for downloading at this site.

Pew Research Center report issued in April, 2015 projects the world religious population through 2050, globally and by country.  Extensive documentation, tables, etc.  See discussion in Key Findings.

Jewish estimates provided are essentially Jews-by-religion (JBR), and do not include Jews who may not identify as Jewish by religion, but may identify for other reasons (family background, secular Jewish, etc.):

• "These projections are based on estimates of people who self-identify as Jewish when asked about their religion on national censuses and large-scale surveys. They do not include so-called “cultural” or “ethnic” Jews – people who
have direct Jewish ancestry and who consider themselves at least partially Jewish but who describe themselves,religiously, as atheist, agnostic or nothing in particular. For the purposes of the religious group projections in this report,
these people are categorized as unaffiliated."

DataBank users should note that the Jewish-by-religion definition and estimates used by Pew in this report are the same as those used in Pew's American Religious Landscape reports.  They differ from the estimates reported in the Pew 2013 Portrait of Jewish Americans, which include secular Jews who identify with being Jewish, but not as a religion.

Worldwide JBR estimate: The worldwide Pew estimate of the number of Jews-by-religion is projected to increase by 16% from 2010 to 2050.  

• The 2010 estimate was 13,860,000; 2020 projection is 14,660,000; 2030 is 15,260,000; 2040 is 15,700,000, and 2050 is projected to be 16,090,000

U.S. Jewish (by religion) population estimates in the Pew tables are expected to decline from 2010 to 2050.  In 2010, the JBR estimate was 5,690,000 in 2010, which is projected to remain essentially steady for several decades, until the JBR population declines to 5,510,000 by 2040 and 5,360,000 by 2050.