"Addition by subtraction"? Or is it more like a "brain drain"?
Not every Catholic is troubled by the church’s dwindling membership. According to some conservative priests and thinkers, the sex scandals and conflicts with the Vatican have shaken out the fair-weather believers. The conservatives want a return to the Latin Mass and an end to challenges to the Vatican’s authority. A return to tradition would likely result in “a smaller but much more fervent and evangelizing church,” says the Rev. John McCloskey, a former Wall Street executive who’s an outspoken advocate of the traditionalist movement. The shrinkage would be only temporary, he says, since as liberals left the church, it would be strengthened by the core of tradition-minded Catholics who obey the church’s ban on contraceptives and rear large families. Such families would inevitably produce more sons, some of whom would enter the priesthood. Thanks to a conservative renaissance, says McCloskey, “the church in America may well be on the cusp of a more vibrant era.” [source]If it's true that 96% of married Catholics use birth control (and apparently the US bishops think this is the case), and if all of those Catholics were to leave the Church, the "tradition-minded Catholics" who remained would have to have some pretty massive families to replenish the Church's numbers.
Somehow I think the hierarchs, who quite like the money they get from the contraceptive-using majority, will find a way to prevent that from happening.