Looking back to events that took place right after the war, it seems to me that Blackbeard likely took Bonney's fruit. At first it looked like Blackbeard targeted Bonney because he knew she was valuable to the government. But the way he hightailed it out of the negotiations the moment he saw Akainu coming for her tells me that the negotiation was likely a bluff to push his luck just a little and also score a ship or something. Really, he had already gotten what he wanted, which was her ability. And that's why it wasn't a huge deal for him to bail out.
Not only would this acquisition bode well for Blackbeard, it would also create a problem for the World Government, since likely they were not interested in a fruitless Bonney. I'm looking forward to seeing how this might play out. I think the WG would go after Blackbeard more vigorously than they behave with other Emperors, and at first it would seem like it is because BB's most dangerous to the world, but really it could turn out to be because they need that particular devil fruit ability back.