Soon Latin America's politics will be undergoing another sea change: an honest-to-God return to civilian rule, replacing the military regimes that have dominated the area all through the 1970s.

Already the signs are there. On Friday, Bolivia's Gen. Hugo Banzer announced that he will not be a candidate for president in the elections to be held next July, two years sooner than previously anticipated. Peru's and Ecuador's governments of generals and admirals are also talking seriously of constituent assemblies followed by presidential elections, perhaps in 1980. Elections were also set recently in Uruguay for November, 1981, and even Chile's Gen. Augusto Pinochet has laid down his timetable. (And if Pinochet talks of these things, then can Argentina's Gen. Jorge Videla and Brazil's Gen. Ernesto Geisel be far behind?)

If the schedules are kept (albeit subject traditionally to too much slippage), South America will be left with only one military dictator in the 1980s, Gen. Alfredo Stroessner of Paraguay, a lonely honor he held before in the early 1960s.

As these developments unfold, they will undoubtedly be welcomed by the Carter administration with applause, and with an overwhelming desire to take credit for Latin America's new democracies.

The desire is understandable, but the temptation should be resisted, for two reasons.

First, because American policy will have had very little to do with the transition to democracy, which will flow from internal problems that the present military regimes have been unable to solve.

And second, because there is no evidence that this next swing to democracy will be any longer lasting than previous such trends. Indeed, all the evidence suggests that we are just going through another cycle, another swing of the pendulum begun long before Jimmy Carter walked down Pennsylvania Avenue. And the only thing as certain as this swing of the pendulum is that there will be a return swing, back to militarism.

And if the Carter administration tries to take credit for one swing of the pendulum, it will risk being struck by the return swing.

RESISTING the temptation to take credit will be especially difficult for the activist Carter administration, which is showing signs of eagerness to claim achievements for its Latin American policies.

As in many other areas, the Carter administration has staffed its Latin America policy desks with young, energetic activists from congressional staffs, like the State Department's Mark Schneider and Sally Shelton, and from the campuses and commissions, like the National Security Council's Robert Pastor. After spending years criticizing the Nixon-Ford people for their alleged insensitivity, if not outright immorality, in dealing with Latin America, they have taken their places in the trenches downtown determined to do better - much better.

But the results are still pretty meager. We have a brace of Panama Canal treaties so carefully crafted they needed a hurriedly concocted "note of clarification" six weeks after the signing; we have several cancelled military agreements with an angry Brazil; we have a rapprochement with Cuba stalled on the predictable issues that still deeply divided us; we have a sugar tariff which promises to do damage to the region's sugar producers - 16 (not counting Cuba) in number.

None of this is surprising; it is merely the natural result of a new, activist administration encountering reality. But the defensiveness with which its officials now respond to criticism, and the growing pressure to show specific results beyong the "reverse body count" of so many political prisoners released, make the coming rollback of military rule a time of testing for the administration.

MILITARY governments in Latin America are in trouble. Peru, for example, has been run by the army since 1968. The government promised a social revolution of the Third World type, and handed the Peruvian people a shattered economy with an enormous foreign debt and the strong possibility of a 40 per cent rate of inflation next year. A similar story of mismanagement could be made for other military regimes, with the possible exception of Chile and perhaps Brazil.

Officers (and civilians) are disillusioned with the military's basic managerial abilities. Worse, serious splits are developing within the ranks of the armed forces themselves - splits which threaten the integrity of the institution itself. In Argentina, for example, the navy is now openly critical of the social costs of the army's (that is, the government's) austerity program. Thus, when the corporate interests of the military are under the gun, their best course is to remove themselves from the main political arena.

Therefore, civilians will be given the reins - for a while - and the officers will be left licking their (often self-inflicted) wounds. For a while - that is the operative phrase. There is nothing in Latin America's long and turbulent history which suggests a permanent change for the better.

Weak civilian regimes, left with problems the military could not solve, will find themselves in trouble too, and once more than military, perhaps a new generation of officers determined not to make the mistakes of their now retired predecessors, will take power in order to save the fatherland.

If the Carter administration has made the mistake of claiming credit for the return of democracy of Latin America, it will now find itself in deep trouble as these new democracies start to falter and fall.

For it is likely that the administration, in its enthusiasm over the renaissance of democracy in the region, will have embraced a number of fledgling regimes and entered into special relationships with them. We will, in effect, have chosen sides, not only between military and civilians, but among competing civilians as well. We will then find ourselves in the midst of the delicate, internal political life of these nations and thereby become identified with one faction in office while alienating all the others out of office.

Moreover, such favored governments will increasingly depends on the United States to keep them in power, and once again, this country will have to mount a vast diplomatic effort to keep our friends in place. Eventually, we will be overtaken by events and, one by one, our friends will find themselves in exile or worse. The generous ones will thank us for our efforts, but more of them will blame us for not doing enough.

It will happen again, because it has happened before. We can minimize the damage by refraining from choosing the path which will prove very tempting to this activist administration eager for visible sucesses.

Perhaps it would help if the administration understood that these swings from civilian to military back to civilian rule are not that bad. They do provide the roughly functional equivalent of a two-party system, with the "ins" managing for a while and, when tired or corrupt or just plain incompetent, being replaced by a fresher, unspoiled set of "outs." With very few exceptions, this military-civilian "two-party" system is working in most of Latin America.

Therefore, to prevent yet another round of overcommitment and its inevitable sense of frustration and despair, this administration's Latin American experts should worry less about showing up their predecessors, and be more modest in their own ambitions. Activism has perils that seasoned men are only too well aware of, and self-justification is the first step on a long trail of bad decisions with which another President and his experts will somehow have to cope.