California’s Supreme Court will rule on Tuesday about the constitutionality of Proposition 8 and the validity of some 18,000 same sex marriages performed in the state last year.

The court announced on Friday morning its intention to issue the ruling, which has been highly anticipated as a June 1 deadline approached.

The conventional wisdom is that the court will rule to uphold Proposition 8 and at the same time uphold the marriages. But since oral arguments were presented in early March, same-sex marriage has been made legal by a court in Iowa and by lawmakers in Maine and Vermont. I’m skeptical that the court will be influenced by the recent momentum in favor of same-sex nuptials, but I’ve been warned that it’s a dicey proposition to try to predict what the court will do in any situation.

Plans are in the works for “Day of Decision” pro-same-sex marriage rallies in East Los Angeles, West Hollywood and Santa Monica, as well almost 70 cities across the country. A “meet in the middle” rally will be held on Saturday, May 30, in Fresno.

Rick Jacobs and his Courage Campaign, which has been training marriage equality activists in “Camp Courage” events, issued a statement: “If the court upholds Proposition 8, the organizations involved in the marriage equality movement will need to determine whether to support placing an initiative on the ballot in 2010 or 2012.

“While the tide is turning nationally, restoring marriage equality to California will not be easy. But we know in our hearts that time is on our side, that justice will prevail, and that equality will be ours.”

The question of when to pursue an initiative on on the state ballot is one that has created some division among same-sex marriage activists — as well as what structure a campaign would take and who would be in charge of running it.

Update: West Hollywood councilman John Duran — a leader in the same sex marriage movement in the state (full disclosure: he married myself and my husband)— issued this statement to constituents: “I think we will not prevail. I hate to be wrong – but I would so like to be wrong this time. I am afraid we will have an evening of protest and anger. I am summoning up the ancestors and spirits from the Mattachine Society and Daughters of Bilitis, through ACT UP and Queer Nation – to be with us on this Prop 8er historic night. May we all be protected with safety and security and with the comfort of knowing that our cause is just and struggle – long. But we will prevail ultimately. From the Castro to Weho, from Hillcrest to Palm Springs, from Santa Cruz to Broadway in Long Beach, from Silverlake to the Russian River – we gather…….”