Hiring a landscaping GM

2 years ago I purchased a residential and commercial landscaping company. Over the next year I will be replacing both the seller ( we agreed to a 3 year term of employment) and I was planning on replacing his general manager. The current GM oversees the crews but very little else. I have looked at other landscaping companies where the GM can sell to clients, keep the crews operating efficiently as well as several other duties so I feel like I could hire someone much more capable. But then that prompts the question, next year when the seller retires and I replace him with a new CEO, what is he going to be focused on. Would appreciate any insights from other landscaping company owners as it relates to hiring "key employees" in terms of how they think about responsibilities, comp, etc.