Well, I'm no constitutional authority, so I'll leave this to those that are. I don't see, however, where the leap can be made from not criminalizing to sodomy to a right to marry.
Maybe it can; I'd need to be persuaded though.
1) Is there a constitutional right for adults to engage in private consensual sex?
2) Does it violate the 14th amendment's guarantee of equal protection to outlaw homosexual sodomy, but not heterosexual--in other words, are homosexuals a specially protected group under the 14th amdt.
The most likely outcome in this case, IMHO, is that the court will decide NO on 1, YES on 2.
If that happens, then immediately suits will pop up demanding marriage for gays, because hetero-only marriage laws discriminate against homosexuals, thus violating the 14th amendment. It's only a matter of time before we have a court that will impose homo marriage on all 50 states.
If the court also says yes on #1, then there will be no basis for state laws against consensual incest, polygamy, prostitution. The logical conclusion will also be to legalize drug use and other "private" activities as well that take place within the home. The court might come up with some bogus justification for not striking down all of these laws as well, but it won't last long. Sooner or later, a future court will use this case to strike down all state laws against anything whatsoever that is done in private.
That is the doomsday scenario, and it should be rather frightening for anyone who believes in the constitution and the rule of law.