Patrick Duffy, who played Bobby Ewing for seven years on "Dallas" but died in last fall's first episode, is returning to the series for the annual "cliffhanger" final episode, May 16 . . .

In making the announcement, CBS Entertainment yesterday also said Duffy would return as a regular next fall. But a spokesman for Lorimar Productions would not confirm . . .

Of course, the mystery is just who Duffy will be when he returns in May (a quick check of Boot Hill out on Southfork might be in order) . . .

Lorimar's Bob Crutchfield insisted yesterday that he had "no idea" of the producers' plans for Duffy . . . whose condition after being hit by a car in the last episode of the season and who it was who murdered him comprised last spring's cliffhanger . . .

"All I know," said Crutchfield, "is that the way Lorimar wrote its release about his return there's no guarantee about next season mentioned in it . . .

"The producers say this will be a really good cliffhanger, the best since 'Who shot J.R.' a few years ago," Crutchfield said . . .

He said "it was Patrick's idea to leave the show a year ago but Lorimar has convinced him to come back. I really have no idea what Patrick's character will be or what the story line is surrounding his return" . . .

Since leaving "Dallas" (the word at the time was that Patrick wanted too much money), Duffy has been seen as a goat in CBS' mini-series "Alice in Wonderland" . . .

On the other hand, "Dallas," which finished second in the season's ratings behind "Dynasty" last year with Duffy, has fallen to seventh in 1985-86 without him . . . Also in the News

Talk show king Larry King will not return to NBC's "NFL '86" this fall . . .

Producers wanted King to conduct interviews in New York each Saturday and then join the on-camera team on Sundays . . .

Last season, his first on the show, King did his Sunday news segment for "NFL '85" from NBC studios in Washington . . .

King said yesterday he turned down the job because, aside from the trip to New York each weekend, it would mean working seven days a week . . .

King, who does nightly interviews for the Cable News Network in addition to his late-night radio show on the Mutual Broadcasting System, said yesterday the weekend chores "would be just too much" . . .

He said he regrets leaving the NBC show: "I enjoyed it very much last year but you've got to cut back sometime" . . .

With King's resignation, "NFL '86" will apparently go with holdovers Bob Costas and Ahmad Rashad plus former New York Giant coach Allie Sherman, who reportedly will discuss the weekly NFL matchups and make predictions. In addition, according to an NBC Sports source, an NBC sportscaster -- such as outspoken Bob Trumpy -- may be added periodically to do commentary . . .

NBC News executives may have something to say about the future of "American Almanac" before the sun sets tomorrow . . .

As you know, NBC News President Larry Grossman was in town earlier this week looking at the latest pilot for the on-again, off-again magazine project . . . and NBC Chairman Grant Tinker reportedly took a look at it Monday . . .

One change already in the works: a new title for the show, which has been something of a public relations disaster so far . . .

Current choice: "Profile" . . . Lots More Dots

Channel 26 says Phil Donahue has agreed to host the "wraparound" for Kelly Burke's powerful documentary, "Drinking and Driving: The Toll, The Tears" . . .

The one-hour program airs May 7 . . .

"CBS Evening News With Dan Rather," which probably should be asking what life will be like in the Nielsen ratings next week, will instead air a five-part series next week on "What Life Will Be Like in the Year 2001" . . .

Each night, one and sometimes two segments of the news program will be devoted to subjects like privacy, medical breakthroughs and life styles at the dawn of the 21st century . . .

Channel Nine won't air that repeat of the 1973 American Film Institute salute to James Cagney until Saturday night at 11:30 . . .

CBS is distributing the Cagney tribute Friday night at 11:45, following the Masters golf highlights (our Chateau Marmont bureau chief, who told us Monday of an 11:30 airtime, has been transferred to the Pocatello bureau) . . .

Captain Airwaves knows what you're thinking, TV Column fans. But Channel 11 in Baltimore isn't airing the Cagney special until midnight, April 18 . . .

Edward J. Pfister, former president of the Corporation for Public Broadcasting, has been named dean of the University of Miami (Fla.) School of Communications, effective April 15 . . .

The school, with a current enrollment of about 600 students, was founded last June from a variety of programs that had been in existence in the Miami liberal arts department since the 1940s. Pfister will be the school's first dean . . .

Pfister was CPB president from 1981 until May 1985, when he resigned following a very public battle with CPB board Chairman Sonia Landau at a very public broadcasters convention in San Francisco . . .

In his salad days, Pfister was a reporter for newspapers in Reno, Nev., and Hackensack, N.J., before embarking on a 25-year career in educational and public television . . .

In his new post as founding dean, Pfister will oversee departments of advertising and public relations, photo communications, motion pictures, speech, journalism and telecommunications . . . And Finally

The folks who produce "Jeopardy!" will be in town April 21 and 22 for a contestant search in this area . . .

The game show airs week nights at 7 on Channel 7 . . .

Today, Channel 7 will launch an on-air promotion regarding the visit, inviting would-be contestants to send in post cards to P.O. Box 311, Washington, D.C. 20044 . . . That's P.O. Box 311, Washington, D.C. 20044 . . .

Post card deadline is April 16, after which 250 cards will be selected at random for the "Jeopardy!" crew to ponder . . .