ROBINSON’S & MAY CO. COMBINE : Future of Robinson’s CEO Suddenly in Limbo : Retail: With May Co.’s Mullen named to top spot of combined stores, Mettler’s new role is uncertain.

The blending of the Robinson’s and May Co. department store chains will mean a bigger job for David P. Mullen, the president and chief executive of May Co. California who will take the top spot at the merged Robinsons-May stores next year.

But for Robinson’s President and Chief Executive Robert L. Mettler, who has become a fixture on the local retail and social scenes since his arrival five years ago, the future is a little less certain.

Mettler and Kenneth L. Wilkerson, Robinson’s chairman, will remain with the combined company, said Thomas A. Hays, president of the St. Louis-based May Department Stores, parent of the two Los Angeles-based chains. However, their roles have not yet been determined, he said.

“While we have a lot of work ahead of us, we are excited by the challenge and opportunity this combination provides,” Mullen said in a statement. He said customers will see better merchandise more attractively displayed and better service because of more sales personnel.

Mullen, 58, and Mettler, 52, both have been responsible for the merchandising and marketing at their respective divisions. At both companies, the chairman’s job is the No. 2 position with responsibility for finance, security and other store operations.

Mullen and Mettler have followed similar career paths, spending virtually all their adult lives in retailing and ending up at divisions of May Department Stores only fairly recently. Mullen joined May as president of its Phoenix-based Goldwaters department store division in 1988. He left the post the same year to take the president’s job at Filene’s, another May division based in Boston.

He became president and chief executive of the May Co. California division in January, 1991.

Mettler came to May in December, 1986, as president of its L.S. Ayres division in Indianapolis. Less than two months later, the parent company announced that he was being transferred to head Robinson’s.

He has been active in philanthropic fund raising and, in 1988, was awarded the National Jewish Humanitarian Award at a fund-raiser for the Denver-based National Jewish Center for Immunology and Respiratory Medicine.

In contrast, Wilkerson has been with May for 22 years. Most of his tenure was spent at May’s Famous-Barr chain in St. Louis.