Elon's statement about this was that Roadster, Model s and Model X buyers profited Tesla and enabled them with the profits to develop the Model 3, that they should be put to the front of the line in buying a Model 3.
Since buying a used car does not fulfill this goal, maybe you will not be sent to the front of the line.
It is not the ownership, but the buying of the car from Tesla that triggers the golden ticket.
Maybe buying a CPO from Tesla will give you the results you want, but perhaps buying from a 3rd party...not so much.