From the Committee for a Responsible Federal Budget's analysis of the Social Security Trustees Report:
The only major "legislative" change that affected Social Security came from the Supreme Court: the Windsor decision which overturned the part of the Defense of Marriage Act that prohibited federal benefits for same-sex couples even if they reside in a state that recognized their marriage. This decision makes more people eligible for survivors' benefits. The report notes that there is significant uncertainty around the estimate of new benefits because rules have not been finalized about how far back a marriage would count -- whether it would start at the time of the Supreme Court decision or when the state legally recognized the marriage, as the Social Security Administration has proposed -- and because it is uncertain how many states will legalize same-sex marriage. (The Trustees assume all states eventually will.) While the decision increases the 75-year shortfall by only 0.01 percent of payroll, the uncertainty surrounding the change means that this area could be a source of future revisions.