New York theater -- raising curtain on better times?

Despite a just-ended season on Broadway that in some ways was disappointing, New York theater is alive and well, and some observers have brighter hopes for the future.

The number of Broadway shows sagged this past 1981-82 season (ending May 31, 1982) -- and even some of the biggest hits are not selling out.

But the revenue from ticket sales set a record as several promising playwrights emerged from the wings of Off-Broadway and some prior season successes continued to do well at the box office. And cheers are greeting the long-awaited news that seven landmark theaters will be returned to the Broadway fold in the not too distant future as part of the commercial redevelopment of Times Square.

Moreover, new studies show that Off-Broadway and Off-off Broadway are enjoying an unprecedented growth in audience attendance in the wake of a vast expansion both in the number of producing companies and theaters. Here, like this past season on Broadway, there have been some disastrous flops. Overall, however, Off and Off-off Broadway is having a renaissance not seen since the 1960s, many experts say.

''The Dining Room,'' ''Key Exchange,'' and the Pulitzer Prize-winning ''A Soldier's Play,'' to name but a few, have been solid successes Off-Broadway. ''Crimes of the Heart,'' another Pulitzer winner, began in a regional theater in Louisville, Ky., moved to Off-Broadway, and this past season opened on Broadway -- just one of a growing list of plays to make this type of transition.

''Dreamgirls,'' the black musical that cost $3.6 million to stage, is selling out even at a whopping top orchestra ticket price of $40. It is also expected to pay its investors back in full by fall, the producers say.

Think of Broadway as 40 playhouses in mid-Manhattan's jangling, neon sign-adorned West Side between 40th Street on the south and 52nd Street on the north, between Sixth and Eighth Avenues on east and west. Then Off-Broadway comprises those theaters with up to 299-seat capacity, regardless of whether they are in Times Square. Off-off Broadway means those theaters with up to a 99 -seat capacity.

As of May 24, 29 shows were playing on Broadway; Off-Broadway had 21, according to the Theatre Information Bulletin, a weekly theater guide. Off-off Broadway had close to 100 shows either recently opened or about to bow.

Although Broadway's past season has been disappointing, the number of Broadway productions rose steadily for the previous three years. And indications from planned openings next season are that they will set a four-year high.

In the 1978-79 season, there were just 50 productions; in 1979-80, the number had jumped to 60; in 1980-81, it was 61, but slipped to 48 this past season. By contrast, the 1927-28 season, the biggest in history, saw more than 250 shows produced. But current producers say it is unfair to make such comparisons without pointing out some major differences in the two eras. ''Old Broadway,'' in fact, faced no competition from television and very little from the silent movies. Also, many of its offerings are now considered contrived and ''artifical'' compared to today's drama.

''Last season was still the second-best year we ever had next to 1980-81,'' maintains George Wachtel, director of research for the League of New York Theaters and Producers, Inc. And in terms of ticket revenue, 1981-82 was the best, grossing an estimated $220 million, up from $146 million in the 1979-80 and $179 million in 1980-81, according to League figures.

Calling the 1981-82 season a ''disaster'' or a ''failure,'' as some pundits have, is ''looking at the season through dark glasses,'' says Bernard Jacobs, president of the Shubert Organization, Inc., a major theater owner and producer. ''The Shubert Organization made more money than ever.'' ''Dreamgirls,'' one of the Shubert shows, has already paid back its investors $2 million after only five months on Broadway, Mr. Jacobs says.

According to Variety magazine, some 9,661,000 Broadway tickets were sold in the first 51 weeks of the 1981-82 season, just short of what were sold for the same period last year - and up dramatically from 6.5 million a decade ago. One key reason for strong ticket sales despite skyrocketing ticket prices is the TKTS theater ticket booth in Times Square. It is here, every day, that producers send tickets that have gone unsold at the box office to be sold for half-price at TKTS.

Alfred de Liagre Jr., the dean of Broadway producers, says that more important than just selling more tickets, TKTS ''has gotton a whole new generation of younger people, who cannot afford box the office prices, interested in the theatre.''

But Mr. de Liagre, whose production of ''Deathtrap'' has thus far run 4 1/2 years, laments the soaring production costs that have helped push up price of tickets--and sees very little, if any, relief from these rising costs in the future.

Unfortunately, rising costs, a major chunk of which is union salaries, have also curbed the number of Broadway productions this season--and could have an effect on the future, observers say.

On the other hand, blaming costs alone would be unfair, de Liagure and others say. Producer Jacobs maintains that the Broadway theater is largely unaffected by national recession and upward spiraling costs, and operates on what he calls ''the creative economy.'' And there can be no getting around the fact that the American theater depends directly on the quality of its playwrights and plays, and this quality, while promising, has not blossomed into excellence in many cases.

At a recent conference on playwrights, Edwin Wilson, drama critic of the Wall Street Journal made the observation that there is, in America today, a large number of ''permanently promising playwrights,'' none of whose work has matured to excellence. But this lack is really nothing new--although without anyone of the stature of a Tennessee Williams or an Arthur Miller, it may be more acute now.

Perhaps nowhere has the lack of quality writing and skyrocketing production costs converged more dramatically than in the recent musical flop, ''The First.'' The musical, about black baseball star Jackie Robinson, was lambasted by some critics and closed shortly after it opened, losing more than $3 million for its investors. Some who worked on the show now say it should have opened out-of-town where its defects could have been seen and corrected. But others point out that one reason ''The First'' did not go out-of-town first was that it was so expensive to do so.

On June 1 of this year, the basic minimum weekly salary for a member of the chorus of a Broadway musical went up to $575. Five years ago it was only $355, prompting some union critics to call the increase both exhorbitant and harmful to the health of the theater. However, the the Actors' Equity Association (AEA), which represents some 30,000 members, vigorously defends its contract demands. Half of AEA's membership doesn't work at all during a given year; only 650 members earned more than $25,000 this past season.

Among the promising developments Off-Broadway and Off-off Broadway, has been the addition in the past two years of eight theaters in the ''Theatre Row'' complex on 42nd Street, West of 9th Avenue--and one block West from where seven new Broadway theatres will be established in the next few years.

Broadway, if it is to survive and flourish, is and must continue to look increasingly to places like Theatre Row for its future writing talent, observers say. But genuine cooperation from all sides--from producers as well as unions--is urgently needed to keep the New York theatre.

Observers say that some producers need to be reminded that when they raise ticket prices of hit shows merely to make a profit, they are also setting into motion a future trend that may hurt them when they have a show that might run a little longer if ticket prices were lower.