The Kennedy Center's 1979-80 theater season, with a blank or two yet to be filled in, will include the first major revival of "West Side Story," the latest London successes of Harold Pinter and Tom Stoppard, and the prospect of Tony Randall in "King Lear" (as the Fool; Anthony Quayle will play Lear).

Six of the 10 plays on next year's Theater Guild subscription list have tentatively been decided, the guild and Kennedy Center officials revealed yesterday.

After a September production still to be announced, the Eisenhower Theater will open Stoppard's "Night and Day," starring Maggie Smith, in early October. A London success this season with Diana Rigg, "Night and Day" is set (like John Updike's novel "Coup") in a Uganda-like African nation under an Idi Amin-like ruler.

After "Night and Day" comes Jean Stapleton in a revival of George Kelly's '20s comedy "Daisy Mayme," about a woman who frees the man she loves from domination by his evil sisters. Stapleton did the play last year at the Totem Pole Playhouse, a summer theater in Pennsylvania run by her husband.

"It's a very good vehicle for her," said Kennedy Center Chairman Roger L. Stevens.

"Mayme" will play for four weeks and be followed, in mid-December, by five weeks of the Quayle "Lear," with Patrick Garland directing and Randall tentatively cast as the Fool. "Lear" will start out at the University of Tennessee in Knoxville, following the pattern of "The Headhunters" and "Rip Van Winkle," two previous Quayle shows that came to the Eisenhower.

Then comes another London import, Harold Pinter's "Betrayal," an account of an adulterous love affair told end-first and beginning-last. "Betrayal," probably with Peter Hall coming here to direct, will open in late January and play through February.

Of the three remaining slots on the Eisenhower's schedule, only one has been booked-a May engagement of Hugh Leonard's "Da" (which originated at the Olney Theater), with Barnard Hughes repeating his Broadway performance as the arden, long-winded Irish father.

"West Side Story", previously announced and then dropped because of conflict in diector Jerome Robbins' schedule, will arrive at the Opera House in January. Although no casting decisions have been made, it will be done as a '50s "period piece." Stevens said yesterday, with Gerald Friedman as director and Robbins as a supervisor paying special attention to the dancing.