So, with all these new characters and groups in the mix, Oda's been making it difficult to see who's actually the real enemy. I'm going to give all these guys a potential threat level to make things easier:
1. Donquixote Pirates: (they basically own the joint)
2. Blackbeard Pirates: Though I think Burgess is too arrogant to give up the chance to beat up a colosseum's worth of warriors rather than just steal the fruit, I think that the BB's will have some sort of appearance and some slight antagonization. If they appear, they're definitely one hell of a threat.
3. CP0: Though they're basically brand new, if they're strong enough to make Law tremble a little, then I'm convinced that they're some tough customers who'll cause some trouble.
4. Bartolomeo: If he's as crazy as they say he is, then he might cause some serious issues. It doesn't seem to me that he'll openly target someone, but if he does, I think it'll be messy.
5. Fujitora: Why is he so far down the list? Well, he seems pretty docile. If anyone's going to order a Buster Call, I don't think it'll be him. Though he's an obvious threat to the Straw Hats and Law, he's not going to cause trouble in the city.
6. Violet: This chick kinda scares me. She "likes" Sanji and seems like she could be pretty dangerous if she doesn't get what she wants. On top of that, she could be connected with Doflamingo somehow.
7. Cavendish: Though not a threat, I think he'll get in the way somehow and piss people off.
Well, that's what I think. You tell me your own ideas.