You probably didn’t hear it first here, but I predict that the court will overrule so-called DOMA (that ought to be called “Defense Against Marriage Act”) but will allow Proposition 8. On essentially the same grounds, States’ Rights. And I think that is essentially the correct decision, little as I like the current court.
In five years, you are likely to see maybe 35 states allowing gay marriage and 15 (mostly southern) not. California will certainly repeal Proposition 8, probably sooner rather than later. And Alabama will go down in flames before they do. But for the federal government to refuse to recognize such state action is utterly intolerable.
Such is my humble opinion. Yours?