I have seen 'secure storage' companies pitch to our management that 5,000 users with @example.com emails already use the personal version of the service offered

I have seen 'secure storage' companies pitch to our management that 5,000 users with @example.com emails already use the personal version of the service offered by the company. Now, I'm wondering if we bought the 'enterprise' version of the service if the same thing would happen to these users. If so, it seems the users ought to be given a choice to convert to the enterprise version or change emails beforehand so they can keep their own personal service intact.