Wall Street experts, including a number of its most outspoken bulls, are expecting a flat market for the rest of the year and are starting to wonder whether the enormous pent-up reserves of institutional cash will return to the securities market anytime soon.

The concerns stem from the continuing sluggishness of corporate earnings reports, unabated high interest rates and broadly gloomy forecasts for the remainder of 1982.

But an even longer-term worry for Wall Street gurus is a concern that the market for both stocks and bonds may be losing investors indefinitely.

Robert Stovall, senior vice president and director of investment policy for Dean Witter Reynolds Inc., thinks Wall Street and the financial community is experiencing a sea change that is remaking investor strategy. In fact, Stovall refuses to predict that investment dollars will return to Wall Street in the immediate future.

As long as interest rates remain high, money market funds and government securities will far overshadow stocks. "These cycles usually run themselves out, but if interest rates don't come down, there is no ball game on Wall Street. People will keep playing this short-term rollover indefinitely," Stovall said.

Robert S. Salomon Jr., managing director and director of stock research at Salomon Brothers, agrees. "Most of us were brought up in an environment that taught us that risk and return were related," he said. "As I look now at the opportunities to invest, it seems to me the highest return comes from the least risk--short to intermediate government securities."

The stock market, Salomon said, "has a continuing problem" that only a sharp rise in inflation, dramatic declines in interest rates or a strong upturn in corporate performance is likely to cure.

Although Wall Street's eclipse has long been a fashionable topic, with the unprecedented level of interest rates at a time of economic stagnation, combined with the basic restructuring of investment strategy, the talk is now being taken seriously.

The large institutions that move markets are ignoring the stock market, carefully hanging on to their cash in quantities unequalled since the Hunt brothers sent tremors across Wall Street more than two years ago.

The public, once unwilling to stray from local banks, savings and loans and brokers, no longer appears worried about sending its investment dollars to money funds and institutions. "We have changed the savings and investment habits of this country," said James Balog, director of research at The Drexel Burnham Lambert Group Inc.

Stovall, for one, admitted that he had thought money market funds were a passing fancy and would simply serve as a "garage" for cash until interest rates came down. "I was wrong," he said. "People have incorporated money funds into their family and business management."

Dean Witter's investment policy committee will only predict a range for the Dow Jones Industrial Average, which closed just under 800 today. For 1982, Dean Witter forecasts that industrials will range from 750 to 950.

It's an analysis that most people on Wall Street buy. There are, to be sure, gains to be made from certain stocks, with analysts touting some technology firms and beneficiaries of "disinflation" such as companies in the food and health care fields, as well as utilities.

"The market can rally and have technical moves at any point in time, but there will be nothing better than trading opportunities, brief in nature," Salomon said.

"It will be three yards and a cloud of dust," said Balog of the flat stock market, noting that the public faces a "summer of recriminations," a heavy dose of gloomy political rhetoric about the state of the economy as the nation nears the 1982 congressional elections. "That does not build confidence among investors. A very nervous market will go nowhere, probably right up through the election."

But so-called technical analysts, such as Richard J. Yashewski of Butcher & Singer Inc., think it would not take much to prompt a major rally. "It wouldn't take much of a kick in the tail to get a rally going because technically the market is ready," Yashewski said. "Even a blip in interest rates might be the catalyst."

He also noted that with each recent downturn in the market, fewer stocks have reached new lows, a sign to Yashewski that "each downside probe is less intense.

"The market has been bottoming in stages and that process still seems to be going on," he said. "The one thing we are most positive about is that we will be seeing a summer rally."