An arbitration panel will announce Thursday whether Metro bus and subway employes must be paid an immediate cost-of-living increases, the three lawyers serving on the panel said yesterday.

The transit workers' demand for a 20-cents-an-hour cost-of-living raise was a key issue in a weeklong wildcat strike that ended Tuesday. Bus and subway service was reported to have operated normally yesterday.

The arbitration panel heard arguments in the cost-of-living dipute yesterday. At issue is a clause in a contract that expired April 30. It states that all provisions of the contract should "remain undisturbed" during arbitration proceedings. Separate arbitration sessions have been scheduled to draw up a new contract.

Local 689 of the Amalgamated Transit Union, which represents about 4,500 Metro employes, contends that the disputed clause requires cost-of-living increases every three months until a new contract is signed. The transit agency argues that such wage boosts would improperly alter the "status quo" and that any such increases may be provided retroactively when a new contract takes effect.

In another development, Metro officials accelerated disciplinary proceedings yesterday against some employes who took part in the strike. A Metro spokeswoman said late yesterday afternoon that 20 workers had been suspended, four receive reprimands and 114 others had been charged with disciplinary offenses but were not yet notified of penalities.

Metro officials have said they expected to interview about 250 employes to determine whether to take disciplinary action against them. Such disciplinary measures may be challenged by the employes through grievance procedures.