The culture still insists on monogamy

I'm afraid not for a long while.  In fact all the negative politics surrounding sex trafficking and underage sex make it very unlikely.  Certain European countries and Canada are more open but I don't see us following suit.  The best we can hope for is neglect of enforcement if it doesn't get too out in the open.  The stories about the banks, under pressure from the feds, cracking down on providers' bank accounts is very disturbing.  In some ways there may be more extra legal harassment and suppression coming. Bad, bad, bad.