Man this was such a bombshell!
Here goes my analysis!
The mysterious Jack is the man that was called back then by that broker. Greg thought the broker was Sheepshead but he actually isn’t! Because that broker was bald in a previous shot, thing Sheepshead clearly isn’t.
And as we saw with his Den Den Mushi Blackbeard sports the same beard as the real Blackbeard now!
Also the bounties! Did you notice all the bounties actually come from somewhere in the past 20 volumes (New World)?
Here are all of them!
Luffy – Chapter 636
Nami – Chapter 655
Zoro – Chapter 635
Sanji – Chapter 609
Usopp – Chapter 744
Brook – Chapter 698
Robin – Chapter 658 (While the hand doesn’t match perfectly it’s the only chapter (considering her clothing) this picture could have been taken)
Chopper – Chapter 654 (The cotton candy is actually Nami’s cloud) (Picture taken in the Sunny’s bath)
Franky – Chapter 636
So, did you see that secret pandaman? ; )