I hope they return to the roots of the series in some ways, while keeping the convenience elements like the flowchart tree. In particular, I'd like ZE3's setting to bear more resemblance to 999 than VLR (a Titanic-copy ship sinking is a much more interesting than a generic warehouse), have more horror elements (VLR was too "sterile" for me, the game overs weren't nearly bloody enough), have more "closure" to individual endings (if only to witness the protagonist's demise instead of having the plot dangle in the air like Tenmyouji's, Quark's or Dio's or Luna's.) and show Akane as an innocent and caring person once again in some timeline.
Also, I hope's it's once again 3DS/Vita, or maybe Android-iOS and PC (Steam) as well. ZE wouldn't really translate well to a desktop console.