Now it can be told that Daniel Barenboim will be conducting "Cosi fan tutte" for the Washington Opera in November 1983, and that Jose van Damm will be singing "Don Giovanni" here in four years. What we don't know (except for the "Falstaff" that was leaked by mistake) is what the Washington Opera will be doing next season.

"Will there be a season next year?" your investigative arts reporter asked Martin Feinstein during a recent intermission at the Kennedy Center. "There will," he said, with an enigmatic smile (which his wife, Bernice, loyally called a happy smile; it may have been both).

So much for fact. Rumors are more interesting. Rumor No. 1: Barenboim is not the only international superstar conductor being wooed by Feinstein, and the company may have one of similar magnitude for its blockbuster production of the 1982-83 season. Rumor No. 2: The company, which was breaking even with fairly routine programming, now has incurred a hefty deficit in its (quite successful) bid for major-league status. Corporate contributions are being eagerly solicited and beginning to flow in. Rumor No. 3: Cancel earlier rumors (not published here). "The Good Soldier Schweik," by Robert Kurka (one of the offbeat masterpieces of American opera) will not be given by the Washington Opera next season or probably in the near future. It may be done by one of the smaller local companies sometime in the next few years. Rumor No. 4: Martin Feinstein will probably announce his next season in about a month--just about the time Washington's opera madness will be revving up again for the Metropolitan's visit.

Finally, it is no rumor at all that the Washington Opera will have trouble bringing back the "Barber of Seville" that was such a hit in the two last seasons. Its stellar cast has been gobbled up by other companies. Soprano Janice Hall is under a two-year contract to do leading roles with the Cologne Opera. Baritone J. Patrick Raftery will be busy in Chicago and Houston, though he may find time for one production early in the season. And tenor Jerry Hadley (who was unable to come back this season), is tied up with the Vienna State Opera. At least, we can say that we heard them in their prime.

Meanwhile, the Met has announced its 1982-83 season, but space will not permit. Perhaps next time.