JJ might be good (this article couldn't convey why in the "What is jj and why should I care?" page) but it's not 10x better than git, so it will likely die. Sorry, nothing personal, Mercurial/hg was a little bit better than git and died too. Network effects.

What has a change is ast-based version control.

You adding a feature to a function that uses a struct I renamed shouldn't be a conflict. Those actions don't confliuct with each other, unless you treat code as text - rather than a representation of the logic.

Ending merge conflicts might make a new version control 10x better than git, and therefore actually replace it.