The project plan is a model of reality as best we can project. It requires monitoring and control after the plan is built and updating to reflect the current reality in the project. Project planning is not a once and done exercise. You will need to re-plan and and adjust throughout the lifespan of the project. Microsoft Project is just one of the tools in the project manager's kit.

If you are monitoring progress in the project and the successor cannot start as planned - revise the plan.