Next season is the Denver Center Theatre’s 25th anniversary. But the theatre’s celebrations will be somewhat muted. The 25th season contains only one premiere, and tight budgets make restraint mandatory. “That premiere is a new musical, but its loneliness in a collection of regional premieres and American revivals points toward the shrinking endowment of the Bonfils Foundation, which largely underwrites the theater company. Donovan Marley, the theater’s artistic director, said next season will also see more staff reductions, and while he hoped they would be through attrition, he could not guarantee it.”