I dont think they will join if they have a crew, it wont happen again as Jimbei.
But for a reason we had that arc. My theory had always been, that Joyboy couldn't reach the previous Poseidon User sincd he was trolling and lost that game, so he had to be a subordinate from a new captain, and for this reason Roger laughed, since Joyboy didnt accomplish his goals because he was playing around lol.