No matter what the Court does, DOMA's expiration date is coming up fast, and we can expect not only federal rights but full faith and credit being extended to marriages entered into in any state.
What we can't bank on is that gay Americans in every state will have the right to marry without sneaking across the border to somewhere more accepting. Without the Court extending constitutional protection to the right to marry, there may, for the rest of our lives, be states that refuse to treat gay and lesbian citizens equally.
You can look at national polls supporting marriage equality and say that gays and lesbians are now powerful enough to get what they want through the democratic process, but that's a very bird's-eye view of the landscape. Take a look at individual states, and you'll understand that in many of them, gay citizens are still viewed as second-class. Unless the Court acts to protect those Americans, this inequality could remain for generations to come.