Tagged info can already constitute a Zettelkasten, since relations exist on matching tags. A wiki is much more advanced and a superset of Zettelkasten functionality.

In light of the "graph"-craze I could imagine that we will hear more of it.

That said, it can be helpful for sourcing all kinds of stuff, but still think it is a hipster fad.

edit: some dictionaries suggest that "outliner" is a fitting translation. I don't think that is true due to the hierarchy outliners seem to require.