I don't think there will ever be a breakdown of the family unit because it's too appealing. We've had all the same temptations thru the ages, well maybe not with porn, but even porn was around in old caveman art.
Homosexuality has the same stuff with it that heterosexuality has, no difference of huge proportions. Homo/vs/Hetero some go one way, some another, and the family will still be standing right there. Yeah, there are now more variations of families with step-parenting, but it's just a bigger pot. The kids are still kids and they can figure it all out and if anything, it just makes them stronger and wiser.