The reality is that there's no such thing as CSS4, and no such thing as CSS3 either: starting with CSS3 the spec was "modularized", meaning it was broken up in a bunch of separate and mostly-independent "modules", which are grouped in a "level" but are specified on their own[0].

So the situation is that TFA talks not about CSS4 but about "Level 4 Selectors" (a draft), talking about "CSS4" is language abuse. The specs I linked are Level 3 specs, but independent of selectors and of one another (columns are a CR, grid is a working draft).

To sum up, your question does not really make sense. Grids and columns are part of "CSS4" insofar as they are part of "CSS3" through being Level 3 specifications, but that's completely meaningless. Level 4 selectors could become recommandations before (level 3) grids reach that state, or not. There's no dependency. (columns are already supported by all modern browsers except MSIE).

I'd recommend using (and abusing) http://caniuse.com/ to see the implementation state of each spec, it's become especially important with modular level 3 specs as implementors are free to add one level 3 spec and ignore an other.

[0] You can see a list of specs at http://www.w3.org/TR/#tr_CSS, note how some Level 3 specs are Recommendations, others are Candidate Recommandations, yet others are Last Calls or Drafts.