Warning: Spoilers For Terminator: Dark Fate
Terminator: Dark Fate may continue from where Terminator 2: Judgment Day left off, but it missed a major strand of connective tissue that would have tied the two more closely together. The Terminator franchise, at this point, is as much of a "choose your own adventure" story as the Halloween movies, with several disparate timelines established by the subsequent films in the series, not to mention the television series Terminator: The Sarah Connor Chronicles.
In the case of Dark Fate, the movie acts as a direct sequel to Terminator 2 while ignoring every other installment of the franchise. In the Dark Fate timeline, a new artificial intelligence known as "Legion" arises to take Skynet's place in the future, with a young woman named Dani Ramos (Natalia Reyes) becoming the new leader of the human resistance. With a new robotic killing machine from the future known as the Rev-9 (Gabriel Luna) hot on Dani's trail, a cybernetically enhanced soldier named Grace (Mackenzie Davis) arrives to protect Dani, along with an aging Sarah Connor and a humanized T-800 dubbed "Carl", played by the returning Linda Hamilton and Arnold Schwarzenegger.
The opening scene of John Connor being killed by Carl makes clear that the ending of Terminator 2 has rewritten the timeline, but that ending also left something in place that would have made the bridge to Dark Fate even more seamless - one which could have tied into the creation of Legion. Terminator 2 establishes that Miles Dyson and Cyberdyne Systems reverse-engineered Skynet from the damaged arm and microprocessor chip from the T-800 sent to kill Sarah Connor in 1984's The Terminator.
These prove to be critical items for Sarah, John, Miles, and the new T-800 to retrieve in their mission to prevent Skynet's creation before Judgment Day arrives. At the end of the climactic steel mill battle in Terminator 2, all the Skynet developmental research in Cyberdyne Systems has been destroyed, along with the pursuing T-1000 and the arm and chip from the first Terminator. Additionally, the new T-800 chooses to sacrifice itself by being lowered into a pit of molten steel in order to completely erase all Skynet tech from history and stop Judgment Day.
However, there's still one appendage of the T-800 that's been left behind. During the battle with the T-1000, the T-800 gets its left arm trapped in a gear mesh, which it is then forced to sever in order to free itself and save John and Sarah. Ultimately, this would leave one last link to the original timeline behind, with the T-800's arm remaining in the steel mill to be discovered just like the last one was. To be sure, the flow from Terminator 2 to Dark Fate doesn't feel disjointed, but incorporating the T-800's arm into the creation of Legion would have created a continuity between the two similar to that of the first two Terminator films.
Though Dark Fate has seen a mixed but overall relatively positive reception compared to more recent installments like Terminator Salvation and Terminator Genysis, the series is likely on ice for the foreseeable future after the disappointing box office performance of Dark Fate. While utilizing the T-800's arm for the birth of Legion would likely have not done much to change that, it would have given Terminator: Dark Fate a more definitive unity with its two predecessors, and further cemented the idea that when it comes to the future, some things are truly set in stone.