From left: Dacre Montgomery, Donnie Yen and Rina Sawayama Getty Images; Lionsgate EXCLUSIVE : Stranger Things star Dacre Montgomery has signed on for an undisclosed role in John Wick spinoff Caine , directed by and starring martial arts legend Donnie Yen as the blind assassin.   Montgomery joins Yen and Rina Sawayama, who will also reprise her role as Akira. While Montgomery’s role and the logline are being kept under wraps, the new film is said to continue Yen’s story arc following the events of John Wick: Chapter 4 , as Caine has been freed from his obligations to The High Table.   Currently in production for Lionsgate, the movie is produced and creatively overseen by the franchise producers who have built John Wick into a billion-dollar grossing franchise: Basil Iwanyk and Erica Lee through their Thunder Road shingle, and Chad Stahelski, who produces through his 87Eleven Entertainment production banner. Keanu Reeves and John Saunders will also produce.…