It still has to get to the State Supreme Court, of course. This is only step one. But if this ruling had gone the other way, the fight would go back to step zero.
Will California be the next Massachusetts? I can only hope. I suppose New York is further on in the process, and I think there may be other states in the pipeline. As long as we get there eventually.
Edited to note: Washington is the other state that's a step ahead of us. The judge who heard the case is based in SF, but he's a Republican appointee (appointed by Pete Wilson), which I find very encouraging. He also quoted the court case that struck down California's law against interracial marriage (CA was the first state to legalize it, in 1948) in support of his ruling, another good sign.
I think it would be particularly good for either CA or Washington to be the next state to legalize same-sex marriage, because then any lawsuits that go to the federal level will start in the 9th Circuit, the federal courts most likely to rule in their favor.