I agree that this is the most likely scenario. I think the gift shop concept art looks great! It would be cool if Sam was there at the counter, but no matter how he is portrayed, there's the risk that he would still comes under scrutiny, so I expect that he will always have "just stepped away" or be "out making new acquisitions" whenever a boat passes by.
ETA: I'm also happy that they chose to still include Trader Sam in the story line, even if he's not physically present.