Diplomats and commentators around the world expect West German foreign policy to shift to the right following the fall from power of socialist Helmut Schmidt but do not foresee a rupture in Bonn's overall support for detente with the Soviet Bloc.

The new government of Christian Democrat Helmut Kohl is likely to have warmer relations with the Reagan administration and other conservative leaderships and to adopt a more hard-line stance toward Moscow, according to a survey yesterday of official and editorial opinion abroad.

Domestic politics, however, are considered likely to prevent Kohl from yielding to U.S. pressure to pull out of the Siberian gas pipeline project or otherwise to curtail sharply links with the East. Even Kohl's conservative partner, Franz Josef Strauss of Bavaria's Christian Social Union, has labeled President Reagan's actions on the pipeline "dilettantish."

Many officials and newspapers expressed regret at the downfall of Schmidt, a prominent leader who served as a spokesman for West European socialism at summits and other international gatherings.

"We always regarded the role of Schmidt as that of a mediator between East and West, and one very important for world peace," a Japanese official said. Britain's left-of-center Manchester Guardian, noting that Kohl is a burly 6 feet 4 inches tall, said: "Exit a great man; enter a large one."

In Moscow, the Kremlin had no official public comment. Privately, however, the Soviets view the switch as negative. They have grown comfortable with Schmidt's Social Democrats, who opened West German relations with the East 12 years ago and have signed a series of treaties with Moscow.

In an indirect sign of the Soviet position, the official news agency Tass stressed portions of Schmidt's remarks Friday in which he urged the new government to honor the 1970 treaty with Moscow and the 25-year economic cooperation accord signed two years ago. The Soviets will be watching Kohl's positions on two issues: deployment of medium-range missiles in Europe and the pipeline. Kremlin officials indicated privately that they do not expect a sharp shift.

Moscow will have a chance this week to learn first-hand about the new government's intentions. Mikhail Solomentsev, premier of the Russian Federation and an alternate member of the Politburo, is scheduled to visit West Germany as a guest of the premier of the state of North-Rhine Westphalia, Johannes Rau. He may meet Kohl and was believed to be carrying a message for him.

Polish newspapers were openly critical of Kohl, suggesting that he would closely follow Reagan's policies. "The White House's shadow has been extended from the Potomac to the Rhine," the government newspaper Rzeczpospolita wrote.

One key indication of Kohl's attitude toward detente will come this autumn, when he decides whether to welcome East German leader Erich Honeker to reciprocate a trip to the East in December by Schmidt.

In London, a senior Foreign Office source saw some pluses in the Bonn changeover for Margaret Thatcher's Conservative government: "Kohl and his people are ideologically a lot closer to Thatcher's views than Schmidt was, particularly on the need for Western solidarity against the Soviet threat and the importance of strengthened defense capabilities." But the official noted that Hans-Dietrich Genscher will remain foreign minister and added, "The reality is that Kohl won't be in a position to change much of anything. Domestic economic concerns will limit spending on defense, and there's no sign of a shift on a specific East-West problem like supplies for the Siberian pipeline."

French Prime Minister Pierre Mauroy also stressed the theme of continuity, saying the switch in Bonn would not affect its close ties with Paris and emphasizing that Franco-German relations were one of the bases of European cooperation. A spokesman for Kohl said the new chancellor plans a short visit to France this month for talks with President Francois Mitterrand.

In Tokyo, senior government officials said they were particularly unhappy to see Schmidt go because he had served as a buffer against Washington in the economic disputes of the past two years.

"West Germany under Schmidt was always one of Japan's best friends as a standard bearer of free trade, especially when Japan was being criticized by other Western countries for economic expansionism," one official said.

In South Africa, Bonn's rightward shift was seen potentially as influencing the negotiations over Namibia in South Africa's favor. Much could depend on the role of Strauss, who has close links with the large number of Namibians of German origin.

The change is not expected to have much impact in Latin America. While Schmidt's party has given financial backing to leftist movements, the government has backed the broad outlines of U.S. policy there.