THE DATE FOR this year's Tony nominations has been set for May 10, which means that the week immediately preceding that Monday will be loaded with last-minute New York openings.

These include the adventurous "Medea," recently at the Kennedy Center's Eisenhower Theater starring Zoe Caldwell and Judith Anderson, now set to bow at Gotham's Cort Theater May 2, and "Nine," with music and lyrics by Maury Yeston to a book by Arthur Kopit, opening the following Sunday, the final date for Tony eligibility.

The latter, which has taken six producers to get onto a stage, is loosely inspired by Fellini's film "8 1/2." That has meant dealing with a covey of Italian lawyers who have represented the Italian director since "8 1/2" stunned moviegoers 19 years back. From the initial staged reading at Connecticut's O'Neill Center, the 46th Street Theater production has ballooned to a cost of $3 million.

More than money rides on this project: Hopeful theatergoers are already anticipating "Nine" as a possible renaissance for American musical theater. If its opening date were delayed, it would likely mean a Tony sweep for "Dreamgirls," the musical tracing the rise of a soul singing group. But, apart from the ingenuity of Michael Bennett's staging and the powerhouse performance of Jennifer Holliday, this show received little praise.

As for "Nine's" night-before-nomination opening, sometimes that can turn out well: Witness, in recent years, "Children of a Lesser God" and "The Shadow Box," which had similarly timed openings.

One complication in the voting will be the Royal Shakespeare Company's "Nicholas Nickleby," eligible in all categories as well as unforgettable. This is not likely, however, to edge out all hope of medallions for "Crimes of the Heart," Beth Hanley's last-season Pulitzer winner thanks to its Off-Broadway production, but which has since moved to Broadway. This year's Pulitzer, Charles Fuller's "A Soldier's Story," is Off-Broadway, thus ineligible for a Tony.

The winners will be announced on the annual telecast of the Tony awards on June 6 at the Imperial, home of those miraculously sliding "Dreamgirls" sets. Even if "Nine" beats it out in the voting, "Dreamgirls" is bound to get a lot of airtime on Tony night from producer Alexander H. Cohen, whose last teleblast was "Night of 100 Stars" for the Actors' Fund.

NOW THAT Dodd, Mead, the 130-year-old New York family publishing firm, has been bought by Thomas Nelson, the Nashville publishing house, what will happen to that invaluable "Best Plays" series?

If these 64 volumes (plus two indices) constitute the bible of the theater world, there is comfort in the fact that Nelson is the land's most active publisher of a perennial best-seller, the Holy Bible.

Jonathan Dodd, latest of the name in the family trade (which will continue under the new ownership), is "bullish, highly hopeful. We're delighted," he said in his lower Madison Avenue office the other day, "that we have this splendid new association, fresh investment money and what I think we've needed badly, a superb marketing department."

Started by critic Burns Mantle in 1919, this series developed in two directions, back to 1899 and forward to last season. While the price has risen from the $2.50 I paid for my first volume back in the '30s to $24.95 for the '80-'81 version, its material has grown to include details of not merely New York theater but hundreds of theaters across America. To theater people the "Best Plays" is what the "Guinness Book of Records" is to ordinary mortals.

Continuing the abridged formula created by Mantle (summations surrounding full-dialogue scenes), these fat volumes now include essays, photographs, production credits about hundreds of theaters and dazzling Hirschfeld drawings, adding up to an authoritative, delicious ramble.

Though the printing order for each edition is 12,500, that's a lot more copies than many a trumpeted book, fiction or nonfiction, ever gets. Some 10,000 are sold immediately, the rest within a few years. No volume is allowed to go out of print, a publishing luxury.

The series, Dodd admits, addresses a limited market, but it's a burgeoning one and he looks to the Nashville firm to push into fresh territory. "Nelson is now headed by Sam Moore, a true book-lover who literally caresses every book he picks up. He will be looking to the bottom line, as publishers have to do these days, but he's aware of the 'Best Plays' cachet."

Editor Otis Guernsey Jr. again makes his picks without help from committees, polls or votes. His choices for the 1980-81 season:

"A Lesson from Aloes," "Amadeus," "42nd Street," "Crimes of the Heart," "Zooman and the Sign," "Translations," "A Life," "The Floating Light Bulb," "Lunch Hour" and "Cloud Nine." Only the first three have been seen here.

Each year, the book also includes a play (chosen by the American Theater Critics Association) that has not had New York production. This year's was "Chekhov in Yalta," by John Driver and Jeffrey Haddow, produced by the Mark Taper Forum. Past ATCA choices have been Marsha Norman's "Getting Out" from Louisville, Michael Weller's "Loose Ends" from Arena Stage and Robert E. Ingham's "Custer" from the Milwaukee Rep.

Dodd, Mead will continue publishing plays as well. On the way is the Stephen Sondheim-George Furth musical, "Merrily We Roll Along," now having its first post-New York failure at Catholic University, and Ernest Thompson's "The West Side Waltz," which will boast a remarkable two-page introduction by Katharine Hepburn, another first for that lady in the year of her fourth Oscar. Thompson's first play, "On Golden Pond," by the way, has just set a record in the paperback field. The New American Library's reprint of the Dodd, Mead original has just hit 249,000 copies. No play of recent vintage has come even close.

WHEN IT COMES to play publishing, the land's largest companies remain Samuel French Inc., established in 1830, and the Dramatic Play Service Inc., created by the Dramatists Guild in 1936. Through them performance rights are channeled to theaters around the world.

Next month a new publishing venture arrives from the Theater Communications Group Inc. of New York. TCG will publish new plays introduced by its members, some 200 nonprofit professional theaters around the country. Founded in 1961 through a Ford Foundation grant and with Arena's Fichandlers as early leaders, TCG is devoted to the sharing of information, experience and ideals.

Pursuing this aim, the group backed a movement titled "Plays in Progress," with Arena participating. The idea was creation of exploratory works, not a few of which have grown beyond their informal roots.

This publishing venture is a logical next step--six plays printed in offset (far cheaper than usual printing methods) and chosen, as dramaturg Michael Feingold puts it, as "among the best plays being produced throughout this country, naturally reflecting this country in all its diversity."

The plays are: Lee Breuer's "A Prelude to Death in Venice," Tom Cole's version of Gogol's "Dead Souls," previously untranslated; David Henry Hwang's "FOB," Emily Mann's "Still Life," Oyamo's "The Resurrection of Lady Lester" and Adele Edling Shank's "Winterplay."

All are exploratory in construction, probing and imaginative, a stimulating reflection of what has come from our relatively recent spread of nonprofit theater. If you've questioned its diversity, these will correct your uncertainty. This first half-dozen is a stirring step up for the trail-blazing Theater Communications Group.