‘Dallas’ Faces a Real-Life Cliffhanger : Television: The cautious producers of the long-running CBS series film a season finale that also can serve as a farewell episode.

The producers of “Dallas,” currently television’s longest-running prime-time entertainment series, don’t know whether their saga about the oil-rich Ewing family will be renewed for fall, so they’re not taking any chances. They’ve filmed a two-hour season finale that can serve as a farewell episode if CBS decides against bringing the soap opera back for a 14th season.

“At best, our status is shaky,” conceded “Dallas’ ” longtime executive producer Leonard Katzman. “There are no guarantees. The show is expensive, and our ratings aren’t what they used to be.”

The top-rated show for the 1980-1981, 1981-1982 and 1983-1984 seasons, “Dallas” currently ranks 56th among the 123 series that the four networks have broadcast this season.

“In the long run, what will determine our fate is not our ratings but our costs,” Katzman said in an interview. “The time comes when the network has to be concerned with whether it’s making or losing money on a show. When you’re No. 1, it doesn’t matter, but when you’re in the middle of the pack, it makes a difference.”

The season finale, tentatively scheduled to air May 10, brings back six former “Dallas” cast members in a plot reminiscent of “It’s a Wonderful Life.” But instead of James Stewart’s decent George Bailey, it will be Larry Hagman’s dastardly J.R. Ewing who reviews his life, with the help of an enigmatic angel played by Joel Grey.

Returning alumni include Linda Gray as J.R.’s long-suffering ex-wife, Sue Ellen; Steve Kanaly as J.R.’s half-brother, Ray Krebbs; Ted Shackelford as J.R.’s younger brother, Gary, and Joan Van Ark as Gary’s ex-wife, Valene. While the latter pair had only to travel from “Dallas’ ” sister show “Knots Landing,” two other characters came back from the dead: Mary Crosby’s Kristin Shepard--the woman who shot J.R. in 1980--and Jack Scalia’s Nicholas Pearce, Sue Ellen’s former lover.

“I think it’s the most unusual show we’ve ever done,” said Katzman, who has some experience in that area: He was the man responsible in 1986 for bringing the supposedly dead Bobby Ewing (Patrick Duffy) back to life in the most famous shower scene since “Psycho,” and deeming the entire previous season to be merely the dream of Bobby’s then-wife Pamela (Victoria Principal).

The episode poses the question: What would the “Dallas” world have been like had there never been a J.R.? “It’s a vision of what would have happened to everyone if they’d never met J.R.,” Katzman said. “Some people are better off and some are worse.”

One notable absentee is Principal, who, Katzman said, “would have done the show, under certain conditions--if she knew it was absolutely the last show. But none of us are ready to concede that it may be.”

The storyline does take that possibility into account, however, as the show’s future may not be decided for anywhere from one week to several months. Regardless of CBS’ verdict, Katzman said, only one ending was filmed.

“I think there’s only one way for ‘Dallas’ to go out, whether it’s the last show or a prelude to the next season,” he said. “We have a ‘go-out’ that stays faithful to our form.”

Does that mean the kind of cliffhanger for which the show is famous?

Katzman, ever true to that “Dallas” form, chuckled. “You’re going to have to guess how we do it.”