Before the Supreme Court punted on Hollingsworth, I thought that this would be the Roe vs. Wade of my generation, the Supreme Court ruling that the Republican Party will spend the next 40 years trying to undo. Abortion will always be an issue, and I think gay marriage will be as well.
Abortion and gay marriage are not remotely the same thing.
Though I lean pro-choice, I will readily admit that the pro-lifers have legitimate claims about "protecting the unborn". Abortion is terminating cells or a fetus that will actually become a human being. Even among the pro-choice crowd, there are huge divides on how far abortion should be permitted to go (example: 1st trimester abortions are generally tolerated, while 3rd trimesters are very much opposed). I'm pro-choice and am deeply uncomfortable with abortion and the procedures. Abortion divides something like 49% - 45% approve/disapprove, while gay marriage is riding high at 53% to 58% approval and rapidly growing favorability.
Gay marriage afects no one except the two getting involved. Abortion has very real impacts and is morally questionable. Gay marriage will be more like slavery and prohibition: resolved, a large majority will be like "no duh" in the future, but it will leave marks on the political landscape for several generations before time makes it irrelevant.
Bad comparison man
It is indeed a bad comparison. When gay marriage eventually is legalized nationally, I have a hard time imagining the GOP actually campaigning on the presidential level to repeal it. All we're in for politically is a bunch more lawsuits about wedding photographers and cake bakers, which will still serve as enough of a wedge issue unto itself. In 2016, the GOP will probably argue it should be decided by the states and leave it off the presidential campaign if they can and if they still have that option legally by then.
On the other hand, abortion as a divisive wedge issue is here to stay for a very long time. Being pro-life is to not believe in giving up.