Jimmy Carter soon will pack his bags and fly off to Georgia and the life of a retired president. But don't expect a similar exodus by King and Spaulding, the Atlanta-based law firm of Carter's former attorney general, Griffin Bell, and of White House confidant Charles Kirbo.

Afflicted by a strain of Potomac fever resistant to the presidential transition, the firm is planning to hire two more persons for the three-lawyer office it opened in June, 1979. Another Atlanta-based firm, Hansell, Post, Brandon & Dorsey, which contributed special assistant Terrence Adamson to Bell's Justice Department staff, plans to triple the number of lawyers at its one-man office here. "The presumption that we are out is laughable," one Atlanta firm member contended.

Sutherland, Asbill & Brennan, which provided the number three person at Justice, Michael J. Egan, plans a 15 percent increase in the staff at its 34-year-old Washington office. And Alston, Miller & Gaines -- as in Philip Alston, Carter's ambassador to Austrailia and partner John L. Moore Jr., chairman of the Export-Import Bank -- also is bulging at the belt. It will add several lawyers to its 12-person staff next year.

Washington already has more lawyers than any other city in the country except New York and perhaps more lawyers per capita than any U.S. city. But that has not slowed the expansion of law firms in Washington.

The number of branch offices here reached 178 last June, an increase of nearly 20 percent over the same time a year earlier. Another 10 have arrived since.

The plans of some California firms -- which, according to conventional wisdom, would be likely to ride Ronald Reagan's coattails to prosperity in the nation's capital -- offer further proof that Washington lawyers apparently answer to a higher authority than the person in the Oval Office. Most of those here already had growth plans before the votes were tallied Nov. 4.

Latham, Watkins, & Hills of Los Angeles, for example, home to former Cabinet member Carla Hills, opened two years ago with 18 lawyers. It will have 23 by the first of the year, 30 by spring and 40 by 1982, according to one knowledgeable source.

"The growth [as a result of political considerations] will be at the margin at best," that source said. "Maybe we'll get some big projects that we might not have gotten anyway. Perhaps we wouldn't be thinking of expanding to 40 or more so quickly." But the firm at the outset leased space for 40 lawyers, fully expecting to reach that number in a few years.

Gibson, Dunn & Crutcher, Reagan's lawyers and the firm of Reagan confidant William French Smith, doesn't expect a drastic expansion as a result of their client's election. Their firm opened here in 1977 with four lawyers and now has 16. The local branch of Jones, Day, Reavis & Pogue of Cleveland, for instance, was reduced to 28 lawyers after a split-off in April, 1979. The heavily Republican firm is now back up to 61 lawyers and expects to add another dozen in the coming year, especially if the economy improves.

The same confidence that is fueling the growth of Washington law offices also is creating fear and uneasiness among Washington-based firms who don't want to lose business with the increasing encroachment of out-of-towners, especially those from New York and Boston.

Kaye, Scholer, Fierman, Hays & Handler of New York opened its Washington office Sept. 1 with four lawyers. There may be 15 by early next year.

Peter Fishbein, liaison partner in New York, says the firm will invest more than $1 million in its Washington branch. Fishbein says Reagan's pledge of fewer regulations on industry does not necessarily mean less work for Washington lawyers, many of whom earn their rent by helping corporations find their way through mazes of regulatory red tape.

"As long as there is a government, the Washington practice is going to be substantial," Fishbein said. Washington is where the great expansion in law firms is going to be, he added, particularly in the fields of telecommunications, international trade, health energy and the environment.

Similar optimism is voiced by Ed Benjamin, partner at Ropes & Gray, based in Boston, who will be coming down soon to open an office with about half a dozen lawyers.

Still, the future is not all rosy. Competition is already fierce and likely to become more intense as various firms, feeling they must open a full-service office in the nation's capital to remain competitive, continue to expand their business here.

One partner in a local firm warned that the days of expansion and high billing may begin to taper off in a couple of years.

"Right now, clients [major corporations, interest groups, foreign governments] have high expectations about what can be done in Washington and they believe we can get things done," he said. "But wait till those expectations aren't realized and those huge legal bills start coming in."