I really doubt that there are any sizable numbers of people that would refuse to enlist because of a ban on gays. After all, gays are not banned NOW: they are just banned from telling anyone about it, which really means telling anti-gays about it. So people who have poorly functioning "gaydar" are thrown out, and others remain.
This might mean that the Marines might have some trouble. If they could let the Marines keep DADT, that could solve the entire problem.Not that I consider this likely. It is unclear whether Marines are even necessary: there is probably nothing they can do that a specialized Army group could not do, after all.
Originally, they were fighting sailors who traveled on boats for specialized coastal attacks. Now everyone gets airlifted, no matter what service, other than the Navy and Coast Guard.
Israel has no ban on gays, by the way.
It is pretty much inevitable that restrictions against DTDT and gays will be lifted, even if you guys do not like it. I am not gay, nor do I have any interest in the military, nor do I know anyone who does.
But it's going to happen, sooner or later. Just like marijuana will be legal, eventually. As those who are opposed dies off, they are replaced by more tolerant people. This is what happened with segregation, womens' rights and a host of other changes in society. Attitudes change, then the laws are changed.
As with segregation, the resistance increases most just before the opposition finally collapses in ruins. This happens in every society.