Yes, but the 9th Circuit granted standing and so did a lower court. One of those rulings will prevail as I understand legal experts. (I am assuming that each court grants or denies standing for itself.) But ... IANAL! :)
Maybe LL will share what he thinks, legally speaking.
Standing is an element of subject-matter jurisdiction (if the plaintiff or appellant lacks standing, there is no "case or controversy" and the case cannot be heard in federal court). So, even if the parties do not raise the issue, SCOTUS will always decide for itself if there is standing at the SCOTUS level, and can review the lower courts' decisions as to standing.
If SCOTUS decides that the appellants lack standing, it can either dismiss the appeal (which will leave the 9th Circuit's decision in place in California, but without any precedential impact on other states), or it can decide that there never was standing even in the lower courts (which will wipe out the lower court decisions). Either way, the Court would avoid a ruling on the merits of gay marriage. That seems to be what Kennedy wants to do: he does not want to be the 5th vote to decide the constitutionality of gay marriage either way. My guess is that he is personally in favor of gay marriage but he would prefer to have it enacted by voters and legislatures rather than imposed by the courts.