When a company moves from an individual incentive plan to a group incentive plan, the company is most likely to experience

higher turnover among high performers

Explanation:

Both the individual and group incentive plans are put in place to encourage to encourage the level of performance expected of the employees by the company around quality and quantity of work done, sales goals, etc. Individual plans do create a very fiercely competitive environment that limits team work and reduce the morale of low-performing employees.  

When companies move away from this type of scheme to a group incentive plan that encourages team collaboration and makes team members to be hold themselves accountable for the performance of the team, there seems to be higher turnover among higher performers.  

This can be mostly achieved through peer pressure by team members. They, in most cases, do notify team members when their performances are below standard to increase their effort.