Agreed. This is all just wild speculation. But since everyone seems to be having so much fun, please allow me to join in.
I suspect the Supreme Court will rule is such a way that essentially legalizes same-sex marriage, but I seriously doubt that religions that regulate marriage among their members will be forced to go along. As someone above already noted, how a religious organization administers it’s sacraments, ordinances, or whatever a particular religion calls it’s rituals is pretty much protected by the Constitution. The Court is interested only in the regulation of civil marriage.
Now, when it comes to applying the law to religious-affiliated institutions such as schools and hospitals that offer their services to the public, there might be a problem. For example, I can envision a Catholic school being prosecuted for discrimination for it’s refusal to hire someone who is party to a same-sex civil marriage.
It’s going be interesting to see how this plays out.