During an interview with MTV Sam Worthington told them what his idea for a Terminator sequel would be, and guess what? It stars out with "we'd go back in time." At that moment, there's a little bit of an eye roll with the expectation that this idea for a Terminator sequel is going to go nowhere, and it really doesn't.
I had an idea that we'd go back in time to when Marcus was first put in jail. They broke Linda Hamilton out of jail in [Terminator 2: Judgment Day], out of the nuthouse. In this one, they'd (John Connor) have to go back in time and break Marcus out of jail. It's the same kind of mirror image. He would be more fallible, because he's human; he's not metallic. He can get hurt. He still has the gung-ho attitude, but he can get hurt now.
Yeah, so this is really nothing mind blowing. He admits that the people he told the idea to didn't really go for it, but that he still thought it was a good idea. I think Worthington is a fun actor to watch up on screen, but as for his creativity in coming up with a new Terminator sequel... I don't think so. He would love to play the character Marcus again, and he's definitely up for starring in a new Terminator film if the "powers-that-be cook up a story [that] was worth telling." I'm sure whatever the studio comes up with won't be any worse than what Worthington's idea was. It's just we've already seen that movie he's pitching, like 3 times, only this time it's all about Marcus. Oh wait! Now I know what he's pitching! A Terminator movie that centers around him. I'll pass.