One Piece provided one of the biggest twists in the series thus far when Blackbeard stole Whitebeard's Devil Fruit after the latter's death, but another major event could connect them again. That is the revelation that Whitebeard, also known as Edward Newgate, never awakened his Devil Fruit, and Teach is going to do it because his personality and motivations are opposite to the late Yonko.
When it comes to Newgate, the One Piece manga made it quite clear that he had everything he ever wanted, which was a family, so that could limit the potential of his Devil Fruit, the Gura Gura no Mi. On the other hand, Blackbeard revels in destruction, and that could be what pushes him to awaken this Fruit, especially considering his role as a villain.
Disclaimer: This theory contains spoilers for the series.
Explaining why Whitebeard didn't awaken his Devil Fruit in One Piece and why Blackbeard will

Dr. Vegapunk stated that Devil Fruits were created out of people's desires and dreams, so an argument can be made that the Gura Gura no Mi was created by someone who wanted to cause destruction. Therefore, Whitebeard never managed to awaken his Devil Fruit because he didn't crave destruction and wanted to protect those he cared about.
On the other hand, Blackbeard is an embodiment of destruction and has enjoyed chaos during his entire stint in the series. So, it wouldn't be exaggerated to claim that he has a personality better suited to awaken the Gura Gura no Mi, especially considering that he is one of the main villains of the manga, so it would be a logical power-up for him.
It also draws a major contrast between the two Yonko, and that is how they treat their crew members. For the most part, Whitebeard served as a protector and viewed his crew as his family while Blackbeard has made it clear that he doesn't care about his members and will easily replace them if they happen to die.
The many mysteries of Blackbeard

There is no denying that Blackbeard, as a character, is one of the biggest mysteries of One Piece. Whether he can use more than one Devil Fruit, his origin and true motivations, or even his role as a villain in the story, many fans are eager to see what author Eiichiro Oda does with this character.
When it comes to his role as a villain, Blackbeard seems like a bit of a wildcard in the grand scheme of things. The World Government, led by Imu and the Gorosei, has established itself as the main threat to the Straw Hats, but Teach could be the one turning things upside down, which is something he has done time and time again across the story.
Final thoughts
One Piece could be setting up Blackbeard for a Devil Fruit awakening as evidenced by this theory, which is something that would make sense given the explanation. Furthermore, it would provide further contrast between him and Whitebeard, adding more subtext to the tragedy of their relationship in Marineford.
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