I think that it'll shift to just being about abortion now since as of yesterday gay marriage is a decided issue, though a few holdouts like Hucksterbee and Pope Frothy will continue pushing for a constitutional amendment most will recognize that it's basically a done deal.
The new "Big Three" social issues will be abortion (that one won't end soon, even if there is a partial or full overturning of Roe- which I think is likely in the next 5-10 years), religious liberty, and drugs.
Religious liberty is just being anti-gay, which the GOP have almost nearly done from the 1970's onwards
And Democrats did until 2009. This issue gained momentum at an alarmingly fast rate, and thankfully it's over.
I didn't even know Obama was opposed to gay marriage until 2012, when he announced he supports it. I really can't believe the Democratic Party was against gay marriage for nearly as long as the Republican Party.