We can be optimistic that monogamy will one day be just one of many lifestyle choices. However, framing the issue as a mere feminist cause with only patriarchical roots is both politically shortsighted and sociologically flawed. Monogamy is a biologically based adaptation as is our proclivity to live in extended social orders. We are genetically programmed toward monogamy to to a certain degree. Even lesbians have monogamous tendencies. It is hard to argue that the whole gay marriage revolution is anti feminist because it promotes monogamy.
It is more productive to frame the argument as changing laws to let individuals make a rational choice for the lifestyles they prefer. I would opt for a polyamorous family but not because of my feminist ideals. I just appear to be disposed to reject sexual jealousy.