Small A Number To Achieve Greatness.

In the 1980s the word was management. The idea was that a manager was needed to create consistency. (The goal was to keep standard from slipping.)
In the 1990s, the key concept was leadership. Because leading by an individual. Organizations saw that leaders were needed because everything was changing so quickly.
In 2000s, the idea is team leadership. Because leading an organization has become so complex and multifaceted, the only way to make progress is to develop a team of leaders.
I think organizations are going to improve greatly as they develop teams, because leadership is so complex. You can't even lead in just one direction -you need the skills to lead up, across, and down! A leadership team will always be more effective than Just  one leader.