@KingofSarus:
I have two random thoughts regarding Luffy's Straw Hat (since Crocodile blew it away… or didn't he?)
Either...
a.) Luffy's Straw Hat will fall in the hearthands of Boa Hancock.
or
b.) The Marines will hold it hostage.
About a) I would say "anyone" can go give the hat back to Luffy lateron, but Hancock is indeed most likely. Oda can play it two ways then. After the timeskip either the marines have decided to disband the shichibukai (and went with pacifista masses to fix their power balance, I mean where else is this plotline leading) and the amazons had to do something about their safety (like relocate) so Hancock can show up to give the hat back and probably join the crew then. That would mean Oda put in the whole "can't leave the shichibukai because of island safety" thing to not make her too obvious of a choice.
The other option is the WG keeps the shichibukai around but fills up their ranks with pacifista who have been given DFs (again, the pacifista plotline has to lead somewhere) and Hancock does a temp visit.
b) no way, it's his trademark, how can the strawhat pirates sail around without Luffy having his strawhat? This is reasoning from a storyteller perspective ofcourse, in reality it makes total sense he might lose his hat somewhere down the line but for the story to lose his trademark, nah.
And on a random note, I wouldn't be surprised if the pacifista are going to become a leading power in the marine/WG army, this would make the most sense for a final villain type deal in a big WG vs Luffy war because they're all machines and Oda can wrap up having people like Coby, Smoker and aokiji being "good marines" in the end.