It is doubtful the court will do anything so sweeping that it would render any Indiana action moot. That would require something like a blanket endorsement of same-sex marriage that all states would be forced to comply with. The court has endured such grief over taking that kind of broad approach on abortion in Roe v. Wade that it’s not likely to repeat the same mistake, especially with the current lineup that leans slightly in a conservative direction.
It’s more likely the justices will take a narrower approach, such as allowing each state to approve same-sex marriages if it wants to, but not requiring other states to recognize them under the Constitution’s full faith and credit clause. (States could also choose not to allow gay marriages, of course.) Such a federalist approach would also argue against the court upholding the Defense of Marriage act.
Until last year, conventional wisdom would have said that four liberal justices would vote to create a “right to gay marriage,” four conservative justices would vote to keep things the same, and the final outcome would depend solely on which side of the bed Justice Anthony Kennedy got up on. But then Chief Justice John Roberts did his surprise switch on Obamacare, so his vote is not quite as predictable as it once was. Now there will be two wild cards in major votes such as these, so be very skeptical of anyone who claims predictive certainty.
The most we can hope for is that the court will let this issue continue to evolve, as it should have on abortion. If the General Assembly acts, Hoosier voters will get a referendum on the amendment in November of 2014. Attitudes are changing on gay marriage, even in conservative Indiana, so that vote won’t be easy to guess, either.