In my opinion the feature Git has always been missing is version control of branches. Of course the immediate consequence would be that you'd be able to roll back changes to branches but there'd be some more fundamental consequences as well. I'm pretty sure some of the problems with GUI's/wrappers around Git break down because there's no tracking of branches/tags.

Besides that it's pretty much endgame in my opinion if you consider only the functionality it's meant to solve. If another "better" VCS would ever become popular I feel it would have to be a drastic change to the way of working with VCS, even more drastic than SVN to Git was. There's some cruft in Git that could probably be taken away, and that would make Git better in a theoretical sense, but in the real world that would never happen (unless we get sideswiped by another industry or platform).