According to The Hollywood Reporter, Yelchin will play a teen version of Reese, the man who fathered world savior John Connor in the original "Terminator" film.
Christian Bale will play John Connor in the time-traveling third sequel to the 1984 sci-fi action film, produced by the Halcyon Co. and set for a Warner Bros. release in summer 2009.
Reese, one of the children who survived a machine-driven nuclear holocaust, befriends Marcus (Sam Worthington), an early edition of the Terminator cyborg played in previous films by Arnold Schwarzenegger.
In Terminator 4, the character is a young version of the one played by Michael Biehn, who traveled back in time in the original to impregnate Sarah Connor (Linda Hamilton) and father the world's future savior.
The film picks up with their son (Bale), now in his 30s, fighting desperately to save a decimated civilization against machines that have taken control. It's unclear if the father and child reunion is only a cyborg motion away in the new film.
Production is scheduled to start in early May.
Terminator Salvation was released May 21st, 2009 and stars Christian Bale, Sam Worthington, Moon Bloodgood, Helena Bonham Carter, Anton Yelchin, Jadagrace, Bryce Dallas Howard, Common. The film is directed by McG.