They won't. Much of the reason for their two-year missionary requirement is to solidify the "us vs. them" mentality at that critical age when young adults often

They won't. Much of the reason for their two-year missionary requirement is to solidify the "us vs. them" mentality at that critical age when young adults often abandon the faith they were raised with. The main strategy for growth of the Mormon church is still raising children as Mormon, retention of young adults, marriage within the church, procreation at higher than replacement rate.