@Crossword:
I guess it could serve as a staging area for the crew to set off again once they're fully reunited, but I don't see it as likely at the moment. What I do despise is that this is just going to give the Hancock joining movement more steam, and that's terrible.
Two things came to mind: One, Luffy hasn't – and we haven't -- learned very much about Haki yet. While I expect Luffy to learn or pickup something about it on the way to or at Impel Down, I would say there is still a possibility of him (or them) returning to Amazon Lily for their traditional end of the arc party where we tend to learn those little details that we were curious about during the arc. Something like that tends to happen, right? Skypiea comes to mind, but perhaps that is the only example. Keep in mind Hancock needs a ride back to Amazon Lily. Even if for some crazy reason she joins, I doubt she will do so without parting ways with her nation. Since she needs a boat back to her island, my guess would be either Luffy (maybe with crew) will return with her and then go to Saboady, or the Kuja Pirates (perhaps with Margaret) will set sail and head to Impel Down in their own way – arriving late -- arriving just in time to pick them up. Or something. IDK there are still possibilities. Not that it makes a huge difference either way. Anyways, moving on.
Two, I would think this gives Hancock less leeway because she cannot just leave her nation when this is all done. If anything, she will either need to maintain her status for their safety or be there to help protect when/if the WG takes issue. I think it is more likely she keeps her position and their nation remains safe myself.
Edit: After reading the chapter, I change my mind. Margaret really came across as the supporting character in this chapter. Especially the way they said their goodbyes. On the other hand, Hancock said she was leaving the nation to the sisters!! This might actually give her an opening to return "someday". Blast! However! Momonga acknowledged her snake as a "somebody" that would be traveling on the ship!! So maybe that's a mark against her….......? lol.