WORD recently spread that the Loews Regency Hotel, which practically coined the term ''power breakfast,'' was closing after nearly two decades. It will reopen, sometime next year, renovated. Until then, regulars at its clubby restaurant, 540 Park, are desperately searching for other tables at which to conduct morning meetings over expensive omelets. Though Jonathan Tisch, the chairman of Loews Hotels, recently announced a plan to recreate its boldface breakfast service at the Park Avenue restaurant two blocks away, it's not immediately clear whether the elite will follow. The hierarchical sightlines (the better to see, and be seen) and history of deal making may not travel well. [ABSTRACT FROM PUBLISHER]