If they are at all visible to the public, and at all accessible, I highly doubt their numbers will dwindle over time because of not having babies. As a warrior society, they will undoubtedly attract plenty of women seeking a different path from getting married & having babies (or being victimized in some way like most women in their society). I expect that their numbers will continue to grow, as long as they aren't shut down by the government (a real possibility, I think).
This isn't the only instance of women organizing to take their power back, and to use that power to defend other women. I am greatly inspired by a group in India called the Gulabi Gang (if I remember right), aka the Pink Saris, a militant group of women who are doing things like helping (fund, protect?) schools for girls, publicly beating up known domestic abusers, and are sending guns to women in Africa.
Its about time we all stopped talking about things like child abuse & rape and expecting some mystical force (the police? the government?) to magically solve these problems for us, and instead started exerting our power to do something about them ourselves. If I knew of a citizen's defense group near me (like the Whatcom county action committee, I think they're called, in Bellingham WA), I would totally join them. Hmm, once I stop traveling around, maybe I should start one!