1.8 Billion Muslims in the World

Islam has developed from the preaching and life of Muhammad, a citizen of the city of Mecca in Arabia in the seventh century of the Christian era. Muslims assert that the main written record of revelation to humankind is the Qur'an, which they believe to be flawless, immutable, and the final revelation of God.
Argument: According to World Network of Religious Futurists there will be 1.8 billion Muslims in the world by 2025, and 2.6 billion Christians.
Questions: How will the increase of Muslims in the world influence the parts of the world with other religions?