The third season is going to be incredible, if it happens. There were no intentions of this being a series finale. It was absolutely a season finale. There's a plan where this can go and it's so good....
You have this episode where John Connor travels to a future where John Connor never existed. I don't know if people completely get it because we work on a string theory, which we've dealt with during the season. We dealt with that with Jessie, in the future that she came from there was Charles Fisher, who tortured everyone. In the future I came from, he never existed. I don't remember him. We were still together within these parallel futures but they were still different and they still had their own paths. This is the same concept. For John Connor to travel to a future where he never existed, where Kyle Reese never left, where Derek and Kyle are still fighting side by side, where Allison (the human Cameron was based on) is still very much present, what becomes of John? What better situation for somebody to grow up in and become the future leader than that? Than to be fighting in what he's been trying to prevent? Not just being the top dog, being listened to for everything, but having to actually listen and follow...
And he clarified that, despite that crackle of lightning at the end, Sarah Connor did stay behind in the present. And John Connor himself may have sent Catherine Weaver back in time to create an alternative to Skynet. He also talks about Derek's undramatic death scene, and how the producers always planned to bring him back in the alternate future. It sounds like if we get a third Sarah Connor season, Derek will be back full time.