...but the TV lights could go out for PBS

''PBS is an endangered species. . .at the very peak of its vigor, vitality, and growth,'' PBS president Lawrence Grossman told an ''emergency press briefing.''

Monitor TV critic Arthur Unger reports the Reagan-proposed $130 million annual budget for the next three years would mean a major cutback in daytime and prime-time programming. ''Sesame Street,'' ''Washington Week In Review,'' and other programs would probably be canceled, according to Mr. Grossman, and some stations would simply go off the air for several hours or even days each week.