Certainly not Compact Flash as the choice. CF is at end of life, bumping up against it's top specification already.
So that only leaves XQD or Cfast 2.0.
In a D4S I'd wish for the new EXPEED4 for whatever improvements that would bring. Off the top I don't have any major wishes bothering me in my D4 for stills. EXPEED4 promises new video-algorhitms and Nikon can always up their game for competitive reasons.