With Cleary Gottlieb Steen & Hamilton moving to a two-tier partnership structure this month, the latest in a line of recent converts, the question becomes what comes next for the dwindling number of major firms that don't have a nonequity tier. At what point do tradition and culture yield to change and progression?

Single-tier partnership firms may now be at a competitive disadvantage with peers because they don't have the same flexibility in hiring talent and lateral groups and in the promotion of senior associates, industry observers say.