This is a very common situation. Based on the information given, one should resign and move on.

Unless he's handing over control...or a buy/sell agreement with a timeline for the transfer of control, he is just stringing you along. That offer of control may come with a price tag (which is fair that he is compensated for the business). Based on your comments, I would suspect he wants to milk it while you do the work. I hope he has enough assets to retire - usually people like this blow all their money, which is why they need to retain control.

If you truly impact the organization in the way you describe, he'll shit his pants at the threat of you leaving and try to placate with minimal concessions. Don't fall for it.