User blog comment:ChopperFan/Blackbeards Vs Strawhats/@comment-3242083-20110319174716/@comment-3242083-20110319180635

No one else has a reason to go after Blackbeard tho. The way it is, there is absolutely no reason for Luffy to engage him. Ace was the one who provoked and lost in a fair battle between devil fruit users.

BB didn't even finish the "job", he could have killed him at any point and still achieve Shichibukai status, but he did not. What would be Luffy's motivation?

Blackbeard killing Thatch? Who the hell is Thatch?

Blackbeard killing Whitebeard? Who the hell is Whitebeard? A temporary ally with no sentimental connection.

I'm 100% sure we will meet the remnants of the Whitebeard pirates again, under Marco's banner. Blackbeard emerged out of their crew, it is a question of honor to hunt him down. I doubt they can pull it off, but the way it is at the moment, there is simply no other candidate with a good enough reason.

However, it could be possible that Shanks engages Blackbeard (or the other way around, actually) and dies (to give Luffy a reason). Oda already presented us the possible matchups between the 2 crews...