Not happening.
If you tax churches, you have to tax all non-profit organizations. The bigger issue, though, is are we going to subject churches to audits and regulations? Are we really going to make regulations which impact the free exercise of religion? There needs to be a separation of church from state. The government shouldn't have a say in a church's accounting practices and what constitutes as a legitimate business expense.
Also, these megachurches that most of us agree are scandalous, could easily absorb the taxes. Heck, they might even recklessly spend, so that the tax liability is greatly reduced. It's the smaller churches, the ones which are actually tied to the communities, which would take the biggest hit. Many of these churches are running on very tight budgets. If you're looking on closing a significant number of churches, then yes, this might be a good policy to implement.
