The Washington Opera announced plans yesterday for its 1978-79 season that will include four operas in four performances each. This is an increase over recent seasons, in which four operas have been given only three times.

The company said that more than 2,000 requests for tickets had to be returned this season for lack of seats.

The operas scheduled for next year are Mozart's "The Abduction from the Seraglio," Bellini's "I Capuleti ed I Montecchi," Donizetti's "Don Pasquale" and Verdi's "Rigoletto."

Principals announced include Silvano Carroli, Mariella Davia and Luis Lima for "Rigoletto"; Ashley Putnam, David Kuebler, Claudette Peterson and Noel Mangin in "The Abduction," Barbara Daniels, Rockwell Blake and Richard Stiwell in "Don Pasquale"; and Tantiana Troyanos, Linda Zoghby and Antonio Savastono in "I Capuleti ed I Montecchi."

"The Abduction," to be sung in English, will be given on Nov. 11, 14, 17 and 19; the other operas will be sung in Italian: "Rigoletto" on Nov. 6, 10, 12 and 16; and in 1979, "Don Pasquale" on April 20, 22, 25 and 28; and "I Capuleti" on April 21, 24, 27 and 29.

Conductors will be Anton Guadagno for "Rigoletto," Reinhard Peters for the Mozart, Theo Alcantara for "Don Pasquale" and Nicola Rescigno for the Bellini.