Can you say this?
"You know, our job (in addition to getting the work done) is to give you a bunch of experiences that you couldn't get elsewhere that are going to make you more valuable. I hope you're here a long time, but if the time comes where you need to cash in on those experiences by moving to another company, that's OK. I hope we can give you the career path, but if not, we'll be better for having you on the team for a couple of years. Maybe you'd even come back when our growth catches up to your career"...
Can you say that?
No? You're not thinking about growing your talent enough. Scared? The other way just gives you false hope. At least with the talent you really want.
Yes? Congrats - they're less likely to leave you than that statement sounds like if you deliver on what you're promising.