U.S. commercial bank failures are expected to decline by about 25% during 1988 after reaching record levels this year, the head of the Federal Deposit Insurance Corp. reported. L. William Seidman told a news conference during the American Bankers Assn. annual convention that about 200 banks are expected to fail by the end of 1987, costing the FDIC more than $2 billion. So far this year, there have been a record 148 bank failures while 11 banks have needed federal assistance to stay afloat. That surpasses all of 1986, when 138 banks failed and seven needed assistance.