The Catholic Church relies on having a sizable number of priests, religious employees of fair-to-middling charisma, unlike the entrepreneurial megachurches, which are typically built by a single superstar preacher.
The glory days of the American Catholic Church in the first half of the 20th Century were built upon the masculine charisma of celibate Irish priests, who typically came from large families, when parents felt assured of getting lots of grandchildren out of their other kids. But in these days of two child families, parents aren't encouraging their sons to become celibate priests.
Banning gays only makes recruiting enough priests an even tougher task. In recent decades, the Catholic Church in America has relied on importing priests from the Third World to make up its existing shortfall, which has generally worsened the charisma problem since many of them don't speak English well. For example, the Vietnamese priest at our parish always tells a joke during each of his sermons. If you listen really hard, they turn out to be pretty funny jokes, but he has never, ever gotten a laugh because his accent is so thick that the parishioners just tune out as soon as he starts his homily.
Two often-recommended steps for the Catholic Church to take is to ordain women and to allow married priests. The first wouldn't work without the second, because if you opened up the priesthood to unmarried women, there would eventually be a large lesbian element among priests, and nobody (especially the straight males who pay a lot of the bills) wants to go to church to be harangued by resentful lesbians.
Lifting the 1,000-year-old requirement for priestly celibacy would make sense for several reasons, both in terms of broadening the pool of potential priests and lessening the chances for sex scandals. The celibacy rule made sense in medieval society as a way to fight nepotism in the Church when those were the best meritocratic positions available, but, today, there are lots of better jobs than in the Church so nepotism isn't much of a problem.
The snag in lifting the celibacy ban is economic: the American Catholic Church doesn't pay enough to support married people with children. New York magazine recently reported that a parish priest in NYC earns $18,000 per annum (although he often gets free housing). Catholics don't have a tradition of tithing 10% of their income.
The Protestant megachurch model is an example of the winner-take-all trend in our economy, where a single charismatic preacher can make a comfortable living for his family by recruiting a vast congregation.
So, it's likely that the Catholic Church will slowly gravitate in that direction, although the Church never does anything quickly.