The Reagan administration yesterday signaled that general revenue-sharing for the cities may not be around after next year.

The $4.6 billion-a-year program of unrestricted aid to local governments is authorized through fiscal 1983, and a budget official said yesterday that no move to strike it from the fiscal 1983 budget, which President Reagan will submit in January, is likely.

But after that, he said, it might fall victim to the fiscal pressures confronting the administration in its drive for a balanced budget by 1984.

The doubtful future of revenue-sharing was raised publicly yesterday by Richard S. Williamson, assistant to the president for intergovernmental affairs, at a seminar on federalism sponsored by the Institute for Contemporary Studies at the Mayflower Hotel.

Answering questions after his speech, Williamson said, "It is no secret that some people in the administration believe that general revenue-sharing is an area to be looked at for further budget reduction, but it would be very premature to speculate on that." Williamson did not expand on his remarks, but the budget official, who declined to be identified by name, readily confirmed that the popular general-assistance program is on the list for possible termination after next year.

General revenue-sharing was the keystone of President Nixon's "new federalism" program when it was inaugurated in 1972, but President Carter and Congress eliminated the state share of it last year, and now the local component appears to be in jeopardy.

The conference heard Sen. Paul Laxalt (R-Nev.), head of Reagan's advisory commission on federalism, say that the administration is determined to end the "degrading" spectacle of state and local officials "going door-to-door in Washington literally begging for a handout."

He said programs shifted from categorical to block grants eventually will be given back to the states for administration, along with revenue sources to support them.

Williamson and Housing and Human Services Undersecretary David B. Swoap cautioned, however, that there is no timetable for such a revenue turnback.

Tennessee Gov. Lamar Alexander (R) renewed the suggestion of several governors that the federal government take over the state share of Medicaid in return for the states' giving up federal aid to education.

But Swoap said the administration believes the states are better positioned to run the welfare program than Washington is.