I am not sure if we will ever be able to replace git with anything else. It is so ubiquitous and just "good enough" for most developers, that the pain of switching to a completely new system would far outweight the benefits. Therefore the only solution that I see is a versioning system that is fully backward compatible with git, maybe just a better API layer on top of git. Facebook tried something similar with Sapling.
For a new versioning system we do not need twenty different choices. We need one free, open, and solid solution that everybody uses.
What the main leaders of the industry should really is to found a groupo that defines that standard. This would be their chance to really make the world a (slightly) better place.