Succession planning is the process of identifying the critical roles within your organization and developing action plans for passing on those roles to others.
As you continue to scale, you are sure to have to move roles around as the expectations of those roles grow more mature and you learn more about each person's abilities, ambitions and limitiations.
Ensuring proper succession planning mechanisms means establishing processes which regularly identify the critical roles within the organization, and document how to excel in those roles in a manner which allows for an efficient and painless transition of the role to someone else.