I honestly doubt that Scopper Gaban would be introduced in such a roundabout way, and I don't think the person Marco is talking to is Izo either. Marco answers in a way as if he is talking to someone who was already on Wano, and knew of the current situation. Izo on the other hand seems to have been picked up by Neko on his way to Wano, which means he wasn't on Wano prior to this. Also, wouldn't Marco's reaction be a bit more happy to see a former fellow crew member. But then that begs the question as to who would be there, that was already on Wano, and knew Marco could potentially be coming there.
Knowing Oda though, it's going to be Izo....