Milestones

RETIRING. Roger L. Stevens, 77, indefatigable chairman and guiding light of the John F. Kennedy Center for the Performing Arts, a position he has held since 1961; in Washington. Stevens, a former real estate magnate and Broadway producer (Bus Stop), shepherded the actual complex into being in 1971. His successor: Ralph P. Davidson, 59, who steps down next year as chairman of the executive committee of Time Inc., and takes up Stevens' duties on July 1.