Gonna be interesting to read Kennedy's opinion on that issue when DOMA's overturned (I'm guessing he'll be given the duty).
I'm not certain it will be overturned. It could be, but I don't see Kennedy as being a sure vote for overturning. It's also possible that it'll be a decision that narrowly strips the Federal government of the power of deciding what a marriage is and leaves the larger issue of whether there is a constitutional right to same-sex marriage for another day.
What you describe is a wholesale overturning of DOMA (or at least sec. 3, which is all that's at issue), so I'm not sure what your point is.
Also, the court cannot decide
Windsor by rejecting a constitutional right to same-sex marriage as that would not answer the question of whether Congress has power to enact DOMA. (The case could be resolved by declaring that the constitution guarantees same-sex marriage, making DOMA clearly unconstitutional, but as that would go beyond the briefs in the case and the holdings of the Circuits, I doubt the court would go there.)