it's a well known fact that the Shichibukai are seven. When one of them resigns (Jimbei), dies (Moria) or goes under arrest (Crocodile) he/she is replaced for another one like Blackbeard, Law and Buggy.
So after the 2 years skip the current Shichibukai are:
Who is missing?
The missing Shichibukai is Edward Weevil, who is introduced in chapter 802.
Edward Weevil, or "Whitebeard Jr." is the self-proclaimed son of Edward Newgate and one of the Shichibukai. His mother is Miss Bakkin, the self-proclaimed lover of Newgate.He was first mentioned by Commodore Brannew in a discussion of the current Shichibukai ranks to several high-ranking Marine officers, but was not explicitly named until after Donquixote Doflamingo's defeat.
(Note this answer is now outdated.)
The anime seems to make a serious point about not revealing who the seventh one is. I doubt it has been revealed yet in the manga. That means the answer is we don't and can't know yet.
That being said the current "shichibukai" are:
Blackbeard left the warlords and is now much more powerful.
`but since doflamingo is defeated and marines arrest him for his evil deeds and law is in alliance with the strawhats. 2 positions for warlords will be vaccant ^__^. i think that was an ressemblance to shiki :)
