To be fully honest, I'm a bit worried that it's too soon for such a ruling. This might well turn into a Roe vs. Wade, abruptly blocking the natural evolution of public opinion and enraging the religious right. So far, there isn't even a clear majority in America that supports SSM... If let things happen normally, chances are that by 2020 that majority will be overwhelming. But if gay marriage is forced down the conservatives' throat by the SCOTUS now, chances are we'll get the same never-ending debates on this, with possibly very bad repercussions on assorted issues such as anti-discrimination laws or adoption.
Sorry for the concern trolling.
Ultimately I don't think gay marriage will end up being an emotional issue on the same line as abortion was and is. Consider for example that a decade ago most liberal politicians (including pro-choice ones) opposed gay SSM, yet now there is virtually no politician who is supportive of abortion rights and opposed to gay marriage but there is a noticeable continigent who hold to the reverse combination (Bob Casey, Joe Donnelly etc.). It'll end up more like laws that legalized no-fault divorce in the long-run-something bemoaned by traditionalists but not something that is absolutely urgent to them like abortion.
