WMAL-AM (630) and WRQX-FM (107.3), the two ABC-owned stations in Washington, will probably remain in the new company that would be created by the proposed $3.5 billion merger of American Broadcasting Companies Inc. with Capital Cities Communications Inc., industry sources predicted.

A source close to Capital Cities said the stations are "fine properties" and that Federal Communications Commission rules limiting multiple ownership of radio and television stations do not affect Washington in this case. ABC does not own a TV station here and Capital Cities does not have a radio or TV outlet, so the new company wouldn't have to divest any local properties if the deal is realized.

"The two Washington stations are very profitable," said an ABC source, adding that the seven ABC programming networks, which are carried locally, are also valuable assets and probably would not be changed.

The reaction at the stations was upbeat. "We have a wait-and-see attitude. But the two stations are very healthy," said one employe, who added that the staffs were relieved and happy after months of rumors of a takeover -- especially those who own some ABC stock, which experienced a healthy rise this week. Gospel Goes

Cal Hackett, a staple of Washington's gospel scene for more than 15 years, has left WUST-AM (1120) for a new job in Baltimore. He had been suspended by WUST management for 30 days because of an internal disagreement, according to Hackett. "I thought I had clarified the misunderstanding," he said. But the station owner wasn't satisfied with his account, Hackett recalled, and suspended him.

Hackett, who started in the 10 a.m. to 2 p.m. shift at WBGR-AM (860) this past Monday, also said he believed it was time for him to move. "I had talked to the current owners about where the station was going. I couldn't see much progress for them or me. I love Baltimore, and it didn't take much convincing for me to move," he said. Washington listeners can usually pick up WBGR.

"Cal is taking advantage of a bigger opportunity," said WUST station manager Lavern Jackson, who declined to discuss the details of the resignation. "He has been Mr. Gospel for 20 years. It is a loss to us, but he has gone as far as he can in Washington." Dorf Dynasty

Soon there will be three Dorfs influencing the local airwaves. Ted Dorf, general manager of WGAY-FM (99.5) and WWRC-AM (980), is now competing with his son Mark Dorf, who joined oldies WXTR-FM (104.1) this week as national sales manager, for the same advertising dollars. And on May 5, Joan Dorf, Ted's wife and Mark's mother, joins WINX-AM (1600) to do a weekly show on contemporary women's issues. Bach to Back

Plenty of Johann Sebastian Bach will be heard everywhere this weekend as his tercentenary is celebrated. WETA-FM (91) will broadcast a "Bach 300th Birthday Celebration," 1 to 5 p.m. tomorrow. WGMS-FM/AM (103.5/570) will air Karl Haas' "The Bach Dynasty" tomorrow from 1 to 2 p.m. Sunday at 2 p.m. it will feature a Bach program from the Boston Symphony. On the Money

WMAL's 12th annual radiothon for leukemia research kicks off at 8 p.m. tomorrow. Bill Mayhugh will host the 24-hour fund-raising drive from the court of the Crystal Gateway Marriott in Crystal City . . . The deadline for registering for Bill Trumbull and Chris Core's third annual Gross National Parade is tomorrow. For $5 per person or $2.50 for children under 12 and senior citizens over 65, local zanies can join the WMAL crowd and the Precision Briefcase Drill Team April 21 and support the D.C. Police Boys and Girls Clubs . . .

Beverly Fox, lunchtime spinner at WLTT-FM (94.7), raised more than $1,000 for the American Heart Association at a recent danceathon . . . The Sixth Annual Irish Coffee Contest with host Gary Murphy of Q-107 netted the Arthritis Foundation $1,500 . . . And WHUR-FM (96.3) raised $8,400 for Southern Africa relief projects last week. Classy Nostalgia

Jeff Baker and David Burd of WCLY-FM (95.5) will host tomorrow's USO Sweetheart Dance, a flashback to the 1940s in music, mood, dances and costumes. The evening at the National Building Museum, commonly called the Pension Building, is from 8 p.m. until midnight. The $18.50 ticket is a contribution to the work of the USO, which has 11 locations in metropolitan Washington. Honors

Rep. Mickey Leland (D-Tex.), a member of th House telecommunications subcommittee, and attorney Henry Rivera, a member of the FCC, were honored here last night by the National Association of Black Owned Broadcasters at its first awards dinner.