..As you may or may not remember, Neo and Trinity both died at the end of The Matrix Revolutions. However, according to our sources,
The Matrix 4 will reveal that their brains were uploaded into the Matrix before their death so they’re able to live on in there, which is how they can return in the upcoming sequel. Apparently, Neo uploaded their brains before they died as a backup in case anything happened and when we see them again, they’ll be stuck in the Matrix and looking a lot older...source:
https://wegotthiscovered.com/movies/neo-trinitys-return-matrix-4-reportedly-revealed/