Ut's already happening. Each year at Easter there are so many converts. Last year the ceremony at our local Cathedral had to be broken into three different days because there were so many converts. That's from one day a couple years ago.
There's another side to this story.
"The U.S. Religious Landscape Survey by the Pew Research Center’s Forum on Religion & Public Life has put hard numbers on the anecdotal evidence: One out of every 10 Americans is an ex-Catholic. If they were a separate denomination, they would be the third-largest denomination in the United States, after Catholics and Baptists. One of three people who were raised Catholic no longer identifies as Catholic."
National Catholic Reporter - The hidden exodus: Catholics becoming Protestants