He means that the changes will be big (a prediction he's willing to make), but that all kinds of unpredictable scientific and sociological things could follow.
And what good is the "science" if it can't make any definitive or useful predictions? You might as well guess.
This guy has plenty of ideas about what could result, and he could make predictions about that. He doesn't know the scope of the changes, other than that they will be grand.
He’s predicting unpredictable stuff will happen and that he thinks it will be big? Anyone can get that far; scientists ought to be able to do better than that. They should be able to get more specific than “It’s going to be big.”
IOW, he’s just guessing.