Consider where the narratives have gone...
In the 1970's, it was free love...
In the 80's it was all about acceptance of the gay lifestyle.
In the 90's, it became all about gay pride.
In the 2000's, it was gay equality.
Now that those battles are over, the narrative has moved to the gender confused.. California just signed into law an act which allows gender confused high school boys to use the girls' locker room, simply because this week they associate with being a girl...
Go ahead and laugh, but the equal protection clause will certainly continue to be stretched, and some of the lines that have been redrawn may wind up being redrawn yet again.
While I'm less worried about NAMBLA's agenda being the next shoe to drop, it wouldn't shock me to see someone move to decriminalize polygamy, or push towards other forms of group marriage. There's already tacit tolerance of polygamy in some parts of the country where law enforcement looks the other way as long as child abuse isn't going on. Certainly, it's a historic practice in multiple religions and cultures....
I'm sure bestiality is safe for now --- both the Sierra Club and PETA would probably have issues with that, and that would confuse liberals far too much.