Terminator timeline

The premise of the story told by the Terminator franchise has changed considerably since the first movie. The actions in the movie and its sequel seem to have altered the course of events in the future, an that's what is visualized in io9's handy timeline overview posted a while back (before both the latest movie and the series finale of The Sarah Connor Chronicles were out, in fact).

The conclusion appears to be that humans are much worse off now than before Skynet started meddling with time. To be sure, the first Terminator movie prophesied a dark and terrible future, but Kyle Reese told Sarah that the resistance (led by John Connor, their son) was close to defeating Skynet, which then as a last-resort measure sent a Terminator back in time to kill Sarah Connor.

In the second movie, Sarah Connor manages to destroy Cyberdyne, the creator of Skynet. But here's the catch: this postponed Judgment Day by a few years, but it also seems to have made Skynet stronger. In both Salvation and Chronicles, the position of the human resistance appears to be a lot weaker than in the original setting. Skynet has stronger weapons and cyborgs, and earlier than it should, and the resistance relies heavily on "converted" Terminators in their bases (some of them even becoming leaders of human crews, such as the submarine captain in Chronicles).

Could it be that that trying to change the future (that is, trying to destroy Skynet before it can be created) actually makes things worse instead of better? It appears that way--so maybe the opposite is true also, meaning that Skynet killing Sarah Connor might by some means have led to a totally Skynet-free future? We'll never know, but it would have made a damn short story, that's for sure.

io9 - 10 Different Timelines From The Terminator Universe