We know for certain that the film will follow Mark Wahlberg’s Cade Yeager in a “man on the run,” type of story, and we know that the mythology of the Transformers will tie into both the legend of King Arthur, hence the trip to the United Kingdom, as well as events in World War II.
We will just have to wait for the film’s first official trailer to really figure out the overarching plot of the movie.
Although Michael Bay has generally kept a fairly high level of transparency on the set of Transformers: The Last Knight, we still have very little understanding as to how the official plot of the film will ultimately play out.
However, beyond that we’re pretty much in the dark.