When Kurt Waldheim's second term as secretary-general of the United Nations expires at the end of 1981, he will in all likelihood be succeeded by . . . himself.
This is the consensus here among senior diplomats from all major ideological and geographical groups.
Although the question of Mr. Waldheim's remaining in office another five years or being replaced does not come up in the public debates during this General Assembly, it is one of the hottest items discussed among diplomats behind the scenes. Many seasoned ambassadors from key countries in the East, West, and South are convinced that:
* The question of who will be in charge of the international organization is too important to be left to last-minute diplomatic maneuvers, deals, and surprises.
* Given the explosive nature of international relations, as well as the potential for new wars and dangerous escalations, it would be wise not to take the stewardship of the UN out the expert and prudent hands of its present secretary-general.
Technically speaking, the secretary-general is chosen by the Security Council and, in the last resort, by the five permanent members of the council who have the right of veto. Any of them can block a candidacy to the office on the 38th floor.
Mr. Waldheim has not publicly expressed a desire to stay at the helm. But according to officials close to him he would not refuse to serve another five years if pressed by leading delegations representing a significant majority of the member states.
While there is no written rule regarding the geographical origin of the secretary- general, there is general acceptance that the next one should be an African or Latin American, since the post has already been occupied by Europeans and Asians -- Trygve Lie, Dag Hammarskjold, U Thant, Waldheim.
The only unofficial candidancy that enjoys a measure of credibility is that of Salim Salim, ambassador of Tanzania who served as president of the 34th General Assembly. But this highly respected, dedicated young African diplomat is suspected by many moderates to be a wolf in sheep's clothing.
In fact, his deeply rooted radical leanings are even less palatable to the Soviet Union than they are to the Western nations. Furthermore, he is opposed by many Francophone Africans and even by some East Africans. Thus Mr. Waldheim is not even seriously challenged.