Those guys are used to be or now still Shichibukai: Crocodile, Dracula Mihawk, Bartholomew Kuma, Donquixote Doflamingo, Boa Hancock, Gekko Moria, Jimbei ,Marshall D Teach, Trafalgar Law.
All of this guys are totally strong enough to be a king in their field. Crocodile was beated by Luffy and put into prision in Impel Down. Gekko Moria also beated by Luffy and then killed by Donquixote Doflamingo after the war. Marshall D Teach now has become the new Yongo in the New World. In order to protect Luffy and Fishman island, Jimbei has lost his Shichibukai position. Bartholomew Kuma was changed by Doctor Vegapunk now only a robot at all. It means that include Law there are only Dracula Mihawk, Bartholomew Kuma, Donquixote Doflamingo, Boa Hancock five Shichibukai right now. From the last chapters, Goverment send a letter to Buggy, I am afraid that this is the invition letter to him and maye Buggy has become the new Shichibukai.
Even though Buggy have no strong power but from the war we can know that most of the pirates know his identify and from the green book of One Piece we even know Buggy own the ability of haki. What a surprise!