To begin, Paramount has announced "Doctor Who" star Matt Smith has joined the cast of their Terminator reboot, aka Terminator: Genesis, playing a new character with a strong connection to John Connor (Jason Clarke), alongside Arnold Schwarzenegger, Emilia Clarke as Sarah Connor, Jai Courtney as Kyle Reese, J.K. Simmons, Dayo Okeniyi and Byung Hun Lee.
Additionally, stuntman Aaron V. Williamson (Captain America: The Winter Soldier) has been cast as a T-800 Terminator, perhaps a younger version of Schwarzenegger's character as Schwarzenegger told MTV "Terminatordeals a lot with time travel, so there will be a younger T-800, and then what that model does later on when it gets reprogrammed, and who gets ahold of him."
Interestingly enough, that might feed into a new rumor coming from HitFix, reporting on a draft of the screenplay they read and how the new film may be incorporating an aged Schwarzenegger into the role of the Terminator. Here's a snippet, and yes, consider it a spoiler:
There is a scene in the script where, literally, we see the scene from the first TERMINATOR film where Arnold steps out, the punks threaten him, he rips [Brian Thompson]'s heart out and takes his clothes and wanders off. And as soon as that scene ends, another Arnold Schwarzenegger who is older and bearded and a very different version of the Terminator walks in from the side and plays another scene right at the scene of that first incident.
I've included the scene from James Cameron's Terminator below for reference.
Terminator: Genesis is directed by Alan Taylor (Thor: The Dark World) and will be released on July 1, 2015.