Trilogy Ltd. and ELXSI reported the completion of their previously announced merger and also said that preliminary figures show a combined operating loss of $7 million for the two companies . . . Caterpillar Tractor said it may lay off more than 900 workers at its Decatur, Ill., plant and shift work done at the plant to other Caterpillar factories or to other companies in the United States or overseas . . . R.J. Reynolds Industries reported that it will cease operation of its R.J. Reynolds Development Corp. subsidiary effective Jan. 1.