Christianity is one of the oldest and largest religions in the world and continues to grow. Many young people of this time keep turning to God as they see the truth in the way things began. Christianity is not soon to fade away, especially as people grow in their faith.
There are 6.9 billion people in the world, and 2.2 billion of them are Christians (2010). That is one third of the world. The second largest religion is Islam at 1.6 billion. But from 2007 to 2014, the Christian population fell from 78.4% to 70.6%. Particularly in America, the Americans who are nonreligious rose from 16.1% to 22.8%!
I'm not entirely certain why this is an opinion question, but okay. The data has shown us time and time again that religion all across the board is in decline. The younger generation has no use nor time for these traditions, so they abandon them to find something that is either more spiritually or intellectually fulfilling. I don't know that there's any data on this, but i'd say that as major religions begin to decline, the number of SBNR will rise.
Unfortunately, many people today have turned away from the church and their christian beliefs because of things such as the bible being against LGBT, deciding to become atheists and sticking to the solid facts rather than spiritual, laziness, or perhaps because of a traumatic experience resulting in them to lose their faith in God, and our savior, Jesus Christ. Although christianity is the world's largest religion, less and less people appear to be going to church and attending regular mass. If you were to take a look at the amount of people who go to church today and compare it to the amount years earlier, you would see a large difference. I have even personally experienced seeing less people at church each Sunday. In fact, most of my friends who I've had religious discussions with have admitted to either being non-religious or atheist.
Let us hope and pray for these people and that one day they will turn back to the christian church and it's beliefs. :)