The Austrian Oak now explains how there will be an older Terminator in the movie, speaking with MTV.
"The way that the character is written, it's a machine underneath," Schwarzenegger stated. "It's this metal skeleton. But above that is human flesh. And the Terminator's flesh ages, just like any other human being's flesh. Maybe not as fast. But it definitely ages."
From that, we can guess that a Terminator goes back in time and ages 30 or so years. There have even been rumors suggesting a Terminator is sent back to the time when Sarah Connor was in her childhood.
Arnold also mentions a younger T-800 model (the version he played in the 1984 Terminator) will be featured, which may suggest some truth to the rumors or speculation that a Terminator goes back in time, but sticks around for 30 years or so in real time.
"Terminator deals a lot with time travel, so there will be a younger T-800," Schwarzenegger added. "And then what that model does later on when it gets reprogrammed, and who gets ahold of him. So it will be all kinds of interesting twists in the movie, but I feel so good."
"Terminator Genesis" has a July 1, 2015 release starring Arnold Schwarzenegger, Emilia Clarke as Sarah Connor, Jason Clarke as John Connor and Jai Courtney as Kyle Reese.