The Supreme Court is poised to rule on two cases related to gay marriage, possibly as early as Monday.

The nation's highest court traditionally hands down rulings before its summer break on cases heard in earlier months. Unless the justices decide to revisit the matter in the fall, the decisions will be released sometime next week, the session's final week.

One case challenges the constitutionality of Proposition 8, California's gay marriage ban, while the other claims the Defense of Marriage Act (DOMA), which prohibits federal agencies from recognizing the legal marriages of gay and lesbian couples, is unconstitutional.

While supporters are preparing win-or-lose events throughout the nation to mark the occasion, opponents are busy planning their next steps.

“There's a sense of anticipation,” Peter Sprigg of the Christian conservative Family Research Council (FRC) told NBC News. “It's likely the decisions will determine the landscape for where we go from here, so I certainly don't believe that the debate is going to be over, but the terms of the debate and sort of the lay of the field, will probably be very different at the end.”

Brian Brown, the president of the National Organization for Marriage (NOM), the nation's most vociferous opponent of marriage equality, and NOM Chairman John Eastman have each renewed calls for a constitutional amendment defining marriage as a heterosexual union.

Eastman said that “every possible scenario and outcome and gambit are being considered because this fight is critically important. If the Supreme Court … manufacturers a right to same-sex marriage out the Constitution, then the remedy would be a constitutional amendment.”

He added that he did not believe that the Supreme Court is “foolish enough to go there,” because “they recognize what harm they've caused to our body politic when they did something similar to that in 1973 and that issue still infects our politics,” he said, referring to Roe v. Wade.

“You can't run for dogcatcher in this country without that issue being part of the campaign,” he said.

Doug NeJaime, law professor at Loyola Law School, said that the possible outcomes vary widely.

“In Perry, the Court has multiple routes open to it: It could rule California's Proposition 8 unconstitutional based on the broad reasoning urged by the plaintiffs' lawyers, the narrow logic employed by the Ninth Circuit, or the middle path put forward by the Justice Department. It could also find that the plaintiffs lack standing to appeal, which would restore the district court's ruling invalidating Proposition 8. Of course, the Court could also rule Proposition 8 constitutional. The path the Court chooses will have significant implications not only for California but for other states across the country,” NeJaime said. In Windsor, the Court is set to determine the constitutionality of Section 3 of DOMA. However, significant jurisdictional and standing questions have arisen in that litigation as well.”

“Looming over both cases is uncertainty regarding the level of scrutiny sexual orientation-based classifications should receive for federal equal protection purposes. Whatever the results, the issue of marriage for same-sex couples will look dramatically different after the Court rules.”

In comments to NBC News, Sprigg lamented that the motivations of opponents such as himself had been misunderstood.

“One of the points of frustration for me has been that the supporters of same-sex marriage want to portray the opponents of it as motivated entirely by hostility towards gay and lesbian people as individuals and that's completely untrue,” he said. “We are concerned about preserving the institution of marriage and making sure it continues to perform the important social functions that it has always performed.”

However, the organization Sprigg represents, the FRC, in 2010 was labeled a “hate group” by the Southern Poverty Law Center (SPLC), which specifically cited Sprigg's anti-gay rhetoric in defending its decision.

(Related: On Hardball, Tony Perkins says FRC against criminalizing gay sex.)