Lucas Black, who was so affable in The Fast and the Furious: Tokyo Drift, has been out of the series ever since that (the third) instalment. The reason is simple: every movie after that actually took place chronologically before that film. It was only at the end of Fast Six that the timelines converged. Which means now Black can return to the fold.
And he will! He's back for Fast & Furious 7... and then up to three more films after that. Fast X? Into space we go!
In Tokyo Drift Black was a troubled American teen living in Tokyo who came under the drift racing tutelage of a sad criminal named Han. During the course of the film Han, who became a major player in the series in parts 5 and 6, is killed in an accident. But the end of 6 reveals it was no accident: Jason Statham killed him! I'm guessing Black's character is signing on for revenge.
The big issue here is that it has been 7 years since Tokyo Drift. Black is no longer that teen, as seen in 42, where he was pretty great as Pee Wee Reese. Maybe we'll just ignore the fact that the character has grown up overnight. It's the Fast and Furious films, after all.