Washington National Opera has had a rough couple of years: the cancellation of its Ring cycle and shortening of its season because of the recession, a rumored merger with the Kennedy Center and the departure of its general director, Plácido Domingo. Even before that, the company’s music director, Heinz Fricke — who had done so much to improve the quality of the Opera Orchestra and conducted so many of its best performances — became ill. Maestro Fricke came less and less often to Washington, and some of the company’s productions languished musically without his much-needed guidance. As rumored this summer and even earlier, Fricke has become music director emeritus, and the man we suspected to be in line to replace him has been officially appointed as new music director.