This is just a random idea:
The film is set thirty years after the human victory over Skynet alluded to in Terminator 2. It ignores T3 and T:Salvation. This future is post-apocalyptic. Humanity has been trying desperately to rebuild, but life has been difficult. Human beings are divided into three groups: those who long for restoration and remember John Connor as a sort of messianic hero, those who live in fear and awe of Skynet and worship the no longer functioning shells of past Terminators, and those who are ambivalent to either belief system and are just survivors.
It is revealed that, before the time displacement machine was destroyed, Skynet used it to send three robots - two Terminators and one Establisher, a sort of Skynet high-tech engineer - into the future to reestablish Skynet. The Establisher would deconstruct one Terminator in order to retrieve the microchip and recreate Skynet technology. The other Terminator is there to protect the Establisher. Now the hero(es) of the story must destroy these Terminators from the past, fighting through those who worship and protect the Terminators to do so.