Consumer credit in the upcoming year will be affected strongly by continued high interest rates, the Federal Reserve's tight money policy and any business recession.

Robert Gibson of the National Foundation for Consumer Credit predicts the availability of funds for nonmortgage loans will be "a good deal tighter in 1980, especially for young persons or those wishing to open new accounts." With the prime rate hovering around 15 percent, banks have complained that their revolving credit accounts are only marginally profitable.

Several have announced they will try either to charge a monthly fee for hitherto free bank cards or raise the interest rate on unpaid balances from 18 percent to 22 percent annually.

Federal credit unions, some of which had to close their loan windows last year when market rates exceeded their 12 percent statutory limit, are urging Congress to raise that ceiling. Present economic conditions already have begun to increase the deliquency rate on consumer loans, a situation that only could worsen if a recession puts more debtors out of work.

According to the Federal Home Loan Bank Board, the availability of funds for mortgage lending is expected to be off by 20 percent in 1980, matching the anticipated drop in housing construction. Although savings deposits will increase slightly, new loans will drop from $100 billion in 1979 to $78 billion. A 35 percent drop is predicted in earnings of savings and loan associations this year.

The board predicts that if the consumer price index dips from its current 13 percent to between 9 percent and 10 percent, mortgage interest rates will decline from their current level of about 12.5 percent nationally to between 11 percent and 11.5 percent.

Next year undoubtedly will mark an important milestone in the evolution away from the fixed-rate mortgage, long the homeowner's primary hedge against inflation. Finalcial regulators have proposed a renegotiated-rate mortgage on which the interest rate is reset every three to five years according to market rates.

FHLBB Chairman Jay Janis said the speed with which this kind of mortgage takes hold depends on customer acceptance, but he added that the fixed-rate mortgage likely will still be around as well by the end of this decade.

Janis described the probable effects of the renegotiated-rate mortgage as a reduction in speculation in housing (and thus perhaps slower price increases) and increased availability of funds. Its proponents also see the rollover as fairer. For every older home-owner who will be deprived of a chance to build up a sizable nest egg thanks to a low-interest, fixed-rate mortgage, theoretically there will be a young, first-time home buyer who can obtain funds at a decent rate. This same principle of fairness is involved in the concomitant creation of savings certificates at rates near those offered to large depositors.

A number of profound changes in banking are on the 1980 horizon. Collectively they constitute a growing trend toward homogenization, as financial institutions invade each other's traditional territory in a quest for the consumer's ever scarcer investment dollar. Already the distinctions between banks and brokers and mutual funds have become blurred because of duplication in services.

Indications are that 1980 will see the beginning of the end of Regulation Q, which sets interest rate ceilings and allows thrift institutions to pay one-quarter percent more than commercial banks in recognition of the thrifts' important role in the financing of residential housing. As the regulation is phased out over a 10-year period, savings institutions are expected to become family finance centers, making short-term consumer loans as well as mortgages. Moreover this will open up the way for rate competition between institutions, much in the way deregulation has spurred airline competition. The Senate has approved such legislation, and the House is expected to take it up again soon.

Also in the legislation is a proposal to allow interest to be paid on checking accounts nationwide for the first time since the Great Depression. Legislation approving these accounts, called negotiable orders of withdrawal (NOW), has a good chance of passage. Savings associations, which never before were allowed to offer checking accounts, will be able to compete with commercial banks which long have been able to do so.

Leading banks and some thrifts have sought authorization to open branches in other states, paving the way for an eventual national banking system. A White House report on branching is expected to be issued later this month.

The blurring between types of financial institutions is also seen in efforts by banks to get Congress to allow them to underwrite revenue bonds, now the province of securities brokers. Banks,on the other hand, have protested the lack of regulation that allows money market mutual funds to give their customers what amounts to checking privileges without having to keep reserve funds against losses on those transactions. A congressional hearing is scheduled for Jan. 24 on the subject.

Other cases of homogenization that may spur official inquiries in the near future include the diversification of insurance companies into mortgage lending, and that of brokerage firms into real estate, mortgage insurance and cash deposit programs offering absolute security at interest rates higher than those paid by banks.