According to a study done by the Pew Research Center 22.8% of Americans do not affiliate with any religion. That’s up from 16.1% in 2007. That’s promising. I would give credit to the internet and the wealth of information out there for this. If that trend continues, the non-religious could be the majority in 50 years. Chances are that the rate will increase and it will happen even quicker.
Here is the study: http://www.pewforum.org/religious-landscape-study/