With the Memorial Day weekend opening of “Terminator Salvation” looming, the future of the franchise has become intriguing.

“Terminator” is the only franchise in which the distributors aren’t locked in for future films.

MGM has a 30-day right of first refusal to finance and distribute the fifth “Terminator” film, a right earned through the settlement of a lawsuit between the studio and Halcyon partners Victor Kubicek and Derek Anderson. According to sources, MGM has every intention of making a serious play for the franchise, potentially trumping Warner Bros., which is distributing “Terminator Salvation” in domestic territories, and Sony, which is releasing the film overseas.

The distribution drama promises to be a real cliffhanger that will begin once Halcyon delivers its demands to MGM along with a first draft of the screenplay for the fifth “Terminator.”

The studio’s position was acquired in the bankruptcy of Orion, which distributed the first “Terminator” film, and the settlement of a lawsuit waged against MGM by Halcyon principals Kubicek and Anderson, who charged the studio with trying to block its “Terminator Salvation” deal with WB and Sony. MGM ultimately had a shot at “Terminator Salvation” but passed.

“Salvation” was a much riskier prospect then than the fifth “Terminator” is now. At the time, MGM made its decision knowing only that franchise linchpin Arnold Schwarzenegger wasn’t returning, and the studio had only an early script by “Terminator 3” scribes John Brancato and Michael Ferris they developed with “T3” helmer Jonathan Mostow. That script has changed significantly, with uncredited work done by Jonah Nolan, Paul Haggis, Shawn Ryan and Anthony Zuiker. Though Halcyon hasn’t yet set a writer for the fifth film, the prospects are strong because McG is returning as director, and Christian Bale will reprise as John Connor.

Halcyon is obligated to give MGM first crack at the fifth film. While some may question whether MGM can afford another big-ticket obligation, “Terminator” would be a strong fit alongside other franchise properties that include two Guillermo del Toro-helmed installments of “The Hobbit,” a Darren Aronofsky-directed revamp of “Robocop,” the next James Bond installment and “The Matarese Circle,” an adaptation of the Robert Ludlum thriller that has David Cronenberg directing and Denzel Washington and Tom Cruise attached to star.

What pricetag would MGM be looking at to get in the game? The third and fourth films each required an investment of approximately $50 million from WB for domestic, with Sony paying in the vicinity of $75 million for overseas rights, which became more expensive on the new film because Sony acquired additional territories from Halcyon, including Japan. Those sums are the negative pickup price and do not include P&A, which they put up separately.

“If ‘Terminator Salvation’ makes good on its current momentum, it will be one of the most sought-after franchises in town, and every distributor will be studying ways to approach the rights holder,” said David Molner, managing director of Screen Capital Intl. “Only time will tell whether pole position is enough for MGM to prevail in that contest.”

It’s unclear whether MGM will come away with the movie; it is uncertain whether MGM has the right to match a deal that Halcyon might make if MGM passes. MGM could be presented with an outlandish budget projection that it might reject, only to watch Halcyon make deals with another studio at a more reasonable rate. MGM has protections against “bad faith” bargaining that could put the studio and Halcyon back in court if another studio received a more favorable deal than MGM was offered.

There are split opinions on whether MGM would be required to take both domestic and offshore territories. Several sources said the studio would need to take both, but other insiders said MGM can take either piece and invite in partners.

The MGM-Halcyon drama may not play out until a year from now, when Kubicek and Anderson get an early script, but the stakes may well be supremacy for summer 2011 or 2012.

Halcyon declined comment, as did MGM.