Visions of millions of dollars in office buildings, hotels, shops, townhouses and condominium apartments clustered around Metrorail stations are dancing through the heads of Northern Virginia developers and planners.

But Santa may be late -- by a year or more in some instances.

Some projects planned in Alexandria and at Huntington in Fairfax County have been put on hold or slowed down, in hopes that the economy soon will grow stronger and an abundance of empty office space will be absorbed.

The four stations--Braddock Road, King Street, Eisenhower Avenue and Huntington--are completed, and tantalizing test runs are being made through them. Metro expects to begin passenger service from National Airport south to Huntington in late 1983 when new subway cars arrive.

Alexandria planners are banking on the rail service to spark a revitalization of the neighborhoods near the Braddock Road and King Street stations. New commercial and residential communities are expected to grow up around the Eisenhower Avenue station, located just inside the Beltway in Alexandria, and at Huntington station, the hilltop terminus of the proposed Yellow Line service in Fairfax County.

Probably the grandest plans have been made for the King Street station. Alexandria officials hope the neighborhood will become a "prime development area" where office, hotel, retail and residential structures worth $250 million to $300 million may eventually cover 2 million square feet, according to Larry Grossman, the city's senior planner.

The focus will be the Metro station and the historic train station belonging to the Richmond, Fredericksburg and Potomac Railroad. Together, Metro and the rail company own about 16 acres of land, including the station sites. They will develop the property as a joint venture and together took bids for construction, said Henry W. Cord, head of Metro's development branch. Cord said the process "has been slowed down" by the sagging real estate market.

The group of developers that won the contract -- a consortium of Alexandria firms calling themselves Station Square Associates -- plans a complex of 894,000 square feet over and around the Metro and the RF&P tracks, said Don Hunt, president of Investment Properties Inc., one of the companies.

The complex, with an estimated value of $100 million, will include a 300-room luxury hotel, some retail shops and 650,000 square feet of office space in "about seven buildings," he said. The complex will conform to the city's 77-foot height restriction -- six or seven stories, depending on the design -- and will not block the view of the nearby Washington Masonic Memorial tower, he said.

Work is not expected to start until January 1985. Although no tenants have been lined up, a few have shown interest and Hunt claims to be "quite bullish on the area." The developers expect to get from $22 to $28 per square foot in office rent, he added.

In addition to Hunt's company, member firms of Station Square Associates include Alexandria developers Eugene Simpson and Brother; VVKR architects, and Tom Sebrell, retired board chairman of United Virginia Bank.

Other buildings are in various stages of planning and construction on land privately held by several owners, said Grossman. Representatives of owners, developers, architects and the city government have been organized into the King Street Task Force, at the instigation of Alexandria planners.

The voluntary group's aim is to maintain some order in development and adherence to a city plan for the area that calls for the 77-foot height limit, mixed use of the property, including some residential units, parking restrictions and landscaping standards.

Grossman said "there is very little speculative office development" in the station area. Most of the construction about to begin or already under way is for new members of Alexandria's growing population of professional and trade associations.

These groups include the National Association of Retail Druggists; the National School Boards Association, which plans to erect a 50,000-square-foot building, and the National Society of Professional Engineers, which is preparing the site for its 60,000-square-foot headquarters.

The Oliver T. Carr Co. will erect two office buildings near the station, with 130,000 square feet of offices and 16,000 square feet of retail shops on two levels of the sloping site. A Carr spokesman refused to discuss details, but hinted that construction could start sooner than next spring, as the company had previously said.

The first Alexandria stop for Metro will be Braddock Road, where the city's nearly bankrupt public housing authority owns the John Roberts Homes, a 40-year-old public housing project. The agency hopes to stave off financial ruin with the proceeds from sale of the project, probably to the city. The city would more than likely hold the land, recently appraised at $5 million, until the property could be resold.

Also next to the Braddock Road station is the 7.29-acre Parker Gray School site, where a $60 million complex called Braddock Place is to be constructed during the next six years. A joint venture including the Savage-Fogarty Companies Inc. plans to put up townhouses; a midrise condominium; 300,000 square feet of office space, and 46,000 square feet of retail shops. In an agreement with the city, the developer has pledged to start work on the project by next May. Development of the John Roberts site may follow, although "we're not sure we can absorb all that office space, and we may have to hold off a while," Grossman said.

Alexandria's last station nestles on Eisenhower Avenue, just inside the Beltway, making it an "exciting" location, says Tom Embrey, executive vice president of the Hoffman Co. The family-owned firm, founded by Hubert N. Hoffman III in the mid-'60s, has approximately 30 "uncommitted" acres around the Metro station. Calling the times "bad for speculative building," Embrey said the company will not plan any office building construction until major tenants are signed up.

The end of the line is the split-level Huntington station. Metro itself is the major landowner, holding 30 acres around the upper level of the station along North Kings Highway. Henry Cord, Metro's development chief, said the site is "ideal for high density residential development and probably some commercial development."

The Fairfax Board of Supervisors is expected to rule sometime this month on a general plan for development at all Metrorail stations planned or existing in the county, opening the way for submission of Huntington construction proposals by next spring, said county planner John Rice. Completed projects are still several years away.