Myra White's Answer:
First, don't try to convince him. Enlist him. As a long term employee he has undoubtedly had career aspirations that remain unfulfilled. See if he is receptive to being the first person you develop a plan for. Obviously you will want to develop a series of questions that surface what he has always hoped he could achieve in his work.
The art of asking great questions is probably best covered off in the use of the Appreciative Inquiry process. If that info is not available, then develop a series of questions that you would ask other employees, (this is where the power plain is flat~everyone gets treated the same) and make him your first executive interview.
Once he sees how it can benefit him, he will see how it can benefit others. Once you know what legacy he seeks to leave; where his passion lies, then completing the follow through to the point where he receives a plan is critical for the credibility of the whole initiative. Few people ask someone about something that matters to them and then actually listen to them. It is the highest honor of respect anyone can receive and is rarely given.
Clearly I don't mean the kind of analytical/logical questions. I mean the kinds of questions that compel a heart-felt answer. It is there that passion and purpose reside.
Secondly, if you can organize employee focus groups into actual discussion groups, then there is an opportunity for employees to come together on the kinds of changes they seek to see. From your bold move above, he may be open to hearing how others in the company see their professional evolution.
This is where his personal communicating style comes in and his security with himself in interacting with the groups. The best thing that can happen is that he shows up to listen. Performance will increase organically simply because when you listen with sincerity, you care. His response to working with his career plan will show you how to best build momentum from there.
If he needs to feel in control and is more likely to tell someone what their career plan should look like, then that approach is far too risky to his reputation and would do more harm than good.
Many companies use employee surveys. The greatest risk is that those surveying the results superimpose their own ideas on top of the data, missing the story that the data tells. Smaller group discussions of a cross section of employees will likely offer more insight.
Turnover rate data tells the story of engagement, leadership and performance gaps and can provide useful information once you have his attention. Keep us posted!