I have noticed diminishing public interest in atheist groups and atheist events, and to be frank, it doesn't bother me. To be honest, I feel somewhat relieved. [laurenelltalk.com]
I think the lack of active Atheist groups simply reflects the trend of people to stop believing in any "religion". I know numerous people, in all adult age groups, who view any "belief/non-belief" philosophy as identical. Possibly a lack of interest in philosophy? Scientific methodology/thought winning out? Or just no longer important to people?
Right, there is an increase in people who consider themselves "non-religious," but they are not latching onto atheist groups. I think it has much to do with atheism really having no core reason to gather.