Updated through online information from Jayson Rodovsky Engquist. -- he Chapel and organ still exist. After Rosemary Hall merged with Choate and moved to Wallingford, Connecticut, the school was sold and operated as Daycroft School (a private boarding school). In about 1990 Daycroft closed and the school was sold and became a Japanese High School (day school) for about 10 years and now it is a Jewish day school. Both of the last owners have promised to maintain the Skinner organ and chapel building. 
Identified through information adapted from E. M. Skinner/Aeolian-Skinner Opus List, by Sand Lawn and Allen Kinzey (Organ Historical Society, 1997), and included here through the kind permission of Sand Lawn:
Extant; unaltered; now the Japanese Educational Institute of New York.