Being non-religious and/or being atheist is becoming more popular and more acceptable and there does appear to be a slow drift in that direction. However, a lot of the shift to non-religious over the past 10 years has been disgust at religious scandals causing the social Christians to switch to non-religious. These are the people who checked Christian on surveys but had nothing else to do with it. These people have not really changed their beliefs or actions, so the real change isn't as pronounced as the surveys suggest.
Jay