Here's why Trinity should be promoted to The One in The Matrix 4. After Neo first meets Morpheus and the gang in 1999's original The Matrix movie, he's ultimately revealed to be a reincarnation of The One - an ancient hero that prophecy foretold would return to save Zion from the Machines. In a later conversation with The Architect, Neo discovers there's much about The One Morpheus wasn't privy to. The One is simply a piece of code carried by a random human plugged into the Matrix, designed to bring stability to the simulation by embodying the natural subversion of the human mind. Neo is apparently the sixth version of The One, but he's the first to break the cycle and refuse to reboot the Matrix.
The Matrix Revolutions ends with Neo and the Machines striking a truce. The One agrees to sacrifice himself and defeat Smith in exchange for peace with Zion. After Smith's demise, the Matrix is rebooted once again, and the simulation is no longer an inescapable prison used for oppressing mankind. The Matrix 4 will continue the story, with Keanu Reeves back as Neo and Carrie-Anne Moss reprising her role as Trinity. It's not yet clear how the pair will be resurrected, nor why their return is necessary, but in the world of the Wachowskis, anything is possible... and this includes Trinity being the next incarnation of The One.
Assuming The Matrix 4 takes place in the aftermath of the original trilogy, the film will be set in an entirely new version of the Matrix, rebooted after Neo's death. Because the Machines and Zion are no longer at war, it's possible that the entire One program was scrapped, but if it wasn't, this means another generation of the fated hero could materialize - and it doesn't have to be Neo. While it is possible that every single incarnation of The One looked like Neo, having Keanu Reeves' face isn't a prerequisite of the job. Regardless of whether Neo and Trinity are physically revived and plugged back into the digital realm, or merely brought back as residual programs, either one of them could be embedded with the code of The One, especially if these two legendary heroes have been brought back specifically to save the world again.
Installing Trinity as The One and Neo as her companion would shake up the dynamic of the original films, offering something fresh for this modern day revival. Instead of Neo once again playing the enigmatic, all-powerful hero plucked from obscurity, he could become more of a mentor, helping Trinity hone the abilities he once possessed. On the other hand, Trinity was always the most badass character in The Matrix, even without powers. It makes narrative sense to let her fly through the air, enter bullet time, and do all the impressive feats Neo got to do in the first three chapters. From an in-universe perspective, Trinity also seems more qualified for the One role than Neo - she's more experienced, more knowledgeable and much tougher.
Trinity was a little let down by the first three Matrix movies, especially with regards to her death. Carrie-Anne Moss' return in The Matrix 4 is already an opportunity to fix that mistake (with or without superpowers), but making her Neo's successor is the most immediate way to redeem Trinity as a character and avoid her becoming a mere accessory to Neo again. More importantly, there's plenty of fun to be had in reversing Neo and Trinity's relationship. Will Neo be a little bit jealous his girlfriend stole his powers? Can Trinity unlock new abilities Neo never used? Is this why Trinity was such a renowned hacker before being unplugged? It may not be what fans are expecting, but Trinity as The One in The Matrix 4 not only opens up new possibilities for her character, but also promises to dig deeper into the mythology and purpose of The One.
