That translation seems incorrect.
Whitebeard only says that Teach is not the man Roger expects, which is obvious.
On the other hand, as
@Erkan12 said, Oda made it clear that finding the One Piece is the end of the story.
Also, the idea that the great war will start after One Piece was always flawed, why would people rebel over a story from 800 years ago? It makes much more sense for them to rebel over something the World Government does in the present. AND THIS IS THE POINT WHERE WE ARE! The great war that Whitebeard predicted will be caused by the transmission of VegaPunk, not by the discovery of an ancient history.
Finally, Oda stated that the ending has not changed since he started drawing. Imu is clearly a character that Oda improvised in the final stage of the series, while Teach has a strong connection with Shanks, who appeared in chapter 1.