Maybe people are starting to realize that all religions are cults. Even the Catholic church started out as a cult, and has become the world's most successful cult.
What is different about mainstream religion is that they are less dangerous and harmful cults than the fundamentalist cults that we are seeing and have been seeing from the 1850-era cults (of which the Watchtower Society is one). The Catholic church is what I term a mild cult--you are not prevented from leaving, and they do little or nothing to stop members from looking at critical material. These milder cults rely heavily on fraud, but do little to cut the members off from mainstream worldly sources.
The harsher cults, like the Jehovah's Witnesses, fit the definition of a full-blown cult. And it's those that use the decline of the other cults and religions as evidence that they have the "truth". This cult in particular not only uses fraud to get people in, but unlike other religions that are milder cults, they also stop people from looking at critical sources or leaving without harsh penalties. And that will ultimately be their demise.
Ultimately, the harsher the cult, the harder they are going down. Religions that rely solely on mysticism will probably last somewhat longer than those that also use force or threat of force. It's only a matter of time before people get p*$@ed off at those cults that use threat of force and leave them, or stop joining. The other religions will be around a while longer, but it wouldn't surprise me if eventually we all become atheists and/or Devil worshipers when people realize what a scam religion is. It will take longer in the South, but I think even the Bible belt will eventually wilt.