The only thing that I can see ever replace git is something that is fully backwards compatible with git and insanely intuitive and possibly extents git or replaces it, but again key thing would be 100% support for regular git repositories, if people enjoy using it with existing git codebases thats step 1. Im not sure if anybody is even trying to engineer such a thing, and lets say they have 100% backwards compatibility with git, what would you change about it to migrate into? Do you keep the same exact underlying git but the commands are more ergonomic somehow? Or are there alternative approaches to how git stores code that could be more efficient somehow?
It takes someone making something better but also compatible with the dominant offering.
Sidenote I had a coworker who worked with people using SVN but he kept a git branch still so he could more easily revert code and experiment, I forget his approach but it seemed to work. I assume the repo from git was a layer above the SVN directory maybe. This goes back to what I am saying though, even though its a little different he was able to still satisfy the needs of the client with their tooling but still use tooling that hes productive on.