When will the Establishment Clause be enforced?

It's not a thing to be enforced, except as against the government (what you're suggesting is against the people). The establishment clause's intent was to protect the church from being controlled by the government, or a church-state marriage, as was occurring in England when our nation was founded. There is nothing about "In God We Trust" which prohibits anyone from worshipping any way they choose, including not worshipping. There is no establishment of any religion in that motto.