In my head, the next two will go as follows:

The next one will be like "The Longest Day," a full-on war film that's like the D-Day invasion of the machines, with everyone armed with a program that'll "de-claw" the machines (since they'd need that apparatus to restore their ruined Earth).  But then when they get there, the main computer tells them that it just sent a Terminator back in time, so John Conner has a "that's it, I'm taking care of this myself!" moment, chucks the thumb drive into his mouth and jumps into the time machine.

The final movie has Old John Conner hunting down the new Terminator (a T-999) that's tracking down his younger self, but then at the half-way point he manages to destroy that machine stone dead, then heads off to destroy the Skynet system, a one-man assault on the Pentagon.  He's gunned down and dies but not before he manages to pacify the baby Skynet program.

Then the powers that be decide to scrap the system and build a new one-- something much fiercer and secure than before.  So when the rights go back up into limbo, the next people who get it (whenever they do) will get to put their own mark on it instead of being saddled with 30 years of continuity.