From the twitter account of Scotus Blog is the first impressions of a knowledgable observer:
Arguments done. #scotus won’t uphold or strike down #prop8 bc Kennedy thinks it is too soon to rule on #ssm. #prop8 will stay invalidated.Kennedy is the key fifth vote and wants to dismiss the appeal, perhaps because of lack of standing since California did not defend the law.
This would mean there is no big ruling, but marriage equality would prevail in California, which is a fairly good outcome. If correct in the prediction, full marriage equality in this nation will be deferred, but considering the court, this may be the best possible outcome now. It comes down to Justice Kennedy.
I'll add more as there are more reports.
Update I: More reports in the same vein, but we likely won't know until June:
Several justices, including some liberals who seem open to gay marriage, raised doubts Tuesday that the case is properly before them. Justice Anthony Kennedy, the potentially decisive vote on a closely divided court, suggested that the court could dismiss the case with no ruling at all.cbsnews
Justice Roberts and "standing." It sounds like Roberts may have raised questions about whether or not private citizens can defend public law. California's Supreme Court and Ninth Circuit both said yes to this question — and it is unusual for federal courts to allow this to happen. This might be why there's growing speculation that the Court might not decide the case: "I don't think we've ever allowed anything like that," Roberts said, according to Reuters. His comments came at the midway point of the arguments, and if the clients lack that right, the Supreme Court may not reach the central question of gay marriage rights.The Atlantic
Justice Kennedy is "uncomfortable." That could mean the Court is leaning toward letting the Ninth Circuit's decision stand.JUSTICE KENNEDY: I just wonder if the case was properly granted.
Update III: My thoughts. If they go this way, it may help in overturning DOMA since roughly 1/8th of Americans live in California. Add in New York and Illinois and Maryland, you have many people living where marriage equality is the law, yet DOMA precludes federal benefits.
Update IV: One day, they will strike all such laws down. The Court is old and full of conservatives. Mortality will change that one day. Justice Kagan decimates the legal argument for bigotry and hate:
Cooper argued that procreation is a vital state interest and that, since same-sex couples cannot have their own children, their marriages do not address this interest. Justice Elena Kagan challenged that argument, asking Cooper whether he would go further and say that state interests would be harmed if same-sex couples were to marry. Cooper said he did not believe that was the correct legal argument.WaPo
The lawyer went on to say that redefining marriage would have real-world consequences that may not be foreseeable but that would include “adverse consequences.”
Kagan asked whether, if procreation were such a vital interest, marriage licences should not be issued to heterosexual couples over 55. Cooper replied that it was rare for both parties to a marriage to be infertile. Kagan retorted: “I assure you if both the man and the woman are over 55, there are not a lot of children coming out of that marriage.”
Update V: From the aptly named, It's the Supreme Court Stupid, in the comments:
Goldstein at SCOTUSblog
The bottom line, in my opinion, is that the Court probably will not have the five votes necessary to get to any result at all, and almost certainly will not have five votes to decide the merits of whether Proposition 8 is constitutional.http://www.scotusblog.com/....
Also, Sotomayor may be angling for a way to get Kennedy to uphold the 9th Circuit without extending things:Second, the Court may dismiss the case because of an inability to reach a majority. Justice Kennedy takes that view, and Justice Sotomayor indicated that she might join him. Others on the left may agree. That ruling would leave in place the Ninth Circuit’s decision.