Forbin's last line in the movie ("Never!" -- spoken to Colossus) is one of resolute, steely eyed defiance.
And for that reason, the ending provides a tiny glimmer of hope for the viewer.
Eric Braeden told a story in an interview, about working on Titanic. At the end of Braeden's scene, after saying "cut," James Cameron said, "Never!" Braeden thought it was a bizarre non-sequitur and assumed it was Cameron's odd way of saying he blew the scene. He was about to get pissed off, but the look on his face must have indicated that he was a little confused." Cameron said, "The last line in Colossus." And then Braeden got that he was being complimented.
Best part of the story is that it confirms the obvious assumption that Cameron was well familiar with this movie before he came up with the Skynet concept. (For all I know he's been very open about it, no idea)