The sudden "revelation" by the California Governor and Attorney General, who say marriage can be eliminated in the future is only news to those who have not thought the issue out very carefully.
Before Christians in California go off and begin a quest for a constitutional amendment, they need to think about a few things.
First, without going into a long theological dissertation, marriage for the Christian is an institution of God. Allowing the state to dictate the terms and conditions of that institution as blithely as American Christians do is a mistake. We’ve already seen that many of those terms and conditions have been changed at law. The opinions of both the Governor and Jr. Brown confirm the obvious: with marriage, what the state gives, the state can take away. (The phrase "rational legislative purpose" is absurd; legislatures do all kind of things for all kinds of reasons, rational and irrational.) The "rights" of civil marriage are in reality very ephemeral, which makes one wonder why some are fighting so hard to obtain them.
Second, in order for a constitutional amendment to be meaningful, it would have to enumerate each and every one of the rights that its proponents wish to preserve, which would make quite an amendment to write, let alone get through the referendum process.
Third, preserving the rights at the state level doesn’t do anything at the federal level. What I specifically have in mind are the provisions of the Internal Revenue Code, which have the stability of Burnham Wood. An example of this is the back and forth on estate and gift taxes, documented here.
Finally, ending civil marriage ends the quest for same-sex civil marriage. This is why proponents of same generally oppose the abolition of civil marriage. It will be interesting to see how advocates of same-sex civil marriage react to this.