Sorry Oda (theory)

Ok I might be completely wrong, but I think this is the direction in which the plot is heading.

Blackbeard has the strongest logia and paramecia fruit, All he needs is the strongest zoan (Luffy has this). So Blackbeard and Luffy will team up and defeat Imu. Once Luffy is tired/down, Blackbeard the opportunist he is will take Luffys fruit.

The ending is non devil fruit Luffy beating 3 devil fruit Blackbeard.