Nones has referred to plain vanilla "unaffiliated," 60% of whom believe in God, if I recall correctly. Many of these folks, including atheists & agnostics, don't believe in the same gods whom we don't believe in. 
Of course, we must do a better job of inviting them to believe in the same God as we do believe in. In that sense, many are not so much post-Christian as they remain pre-Christian.